Digital Transmission Quiz and Flashcards: Asynchronous, Synchronous, and Isochronous

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Questions and Answers

What is the main advantage of parallel transmission over serial transmission?

Improved reliability

Increased transfer speed (correct)

Cost-effectiveness

Reduced number of communication lines

What is the primary disadvantage of parallel transmission?

Higher cost (correct)

Slower transfer speed

Reduced reliability

Increased complexity

What is the purpose of conversion devices in serial transmission?

To increase transfer speed

To reduce cost

To convert parallel data to serial and vice versa (correct)

To improve reliability

What is the main advantage of serial transmission over parallel transmission?

Reduced cost Signup and view all the answers

How many subclasses of serial transmission are there?

3 Signup and view all the answers

What is the primary limitation of parallel transmission?

High cost Signup and view all the answers

In parallel transmission, how many bits are sent with each clock tick?

Multiple Signup and view all the answers

What is the primary difference between parallel and serial transmission?

Number of communication lines Signup and view all the answers

What is the main difference between asynchronous and synchronous transmission at the byte level?

Asynchronous transmission sends bits one after another with start and stop bits Signup and view all the answers

What is the purpose of start and stop bits in asynchronous transmission?

To identify the start and end of a byte Signup and view all the answers

How many bits are used to represent a byte in asynchronous transmission?

8 bits Signup and view all the answers

What is the total overhead data bits required for 160000 bit data transmission?

60000 bit Signup and view all the answers

What is the efficiency of 20KB data transmission using asynchronous transmission method?

73% Signup and view all the answers

Which of the following is an advantage of synchronous transmission?

It is faster Signup and view all the answers

What is the responsibility of the receiver in synchronous transmission?

To group the bits into bytes Signup and view all the answers

What is a natural application of asynchronous transmission?

The connection of a keyboard to a computer Signup and view all the answers

What is the main advantage of synchronous transmission over asynchronous transmission?

It is faster Signup and view all the answers

In which layer of the OSI model is byte synchronization accomplished?

Data link layer Signup and view all the answers

What is the total overhead data bits required for 160000 bit data transmission in the given example?

8000 bit Signup and view all the answers

What is the efficiency of the 20KB data transmission using Synchronous transmission method in the given example?

95% Signup and view all the answers

What is the main difference between synchronous and isochronous transmission?

Isochronous transmission has a shorter time interval between blocks Signup and view all the answers

What type of data is collected in isochronous transmission?

Both synchronous and asynchronous data Signup and view all the answers

Why does synchronous transmission fail in real-time audio and video applications?

Due to uneven delays between frames Signup and view all the answers

What is the rate at which TV images are broadcast in the given example?

30 images per second Signup and view all the answers

What is guaranteed by isochronous transmission?

That data arrive at a fixed rate Signup and view all the answers

What is the primary advantage of isochronous transmission in terms of transmission speed?

It is much higher than asynchronous transmission Signup and view all the answers

What is the purpose of a hold circuit in a PCM decoder?

To hold the amplitude value of a pulse till the next pulse arrives Signup and view all the answers

What is the minimum bandwidth required to transmit a 4 kHz low-pass analog signal?

4 kHz Signup and view all the answers

What is the minimum bandwidth required to transmit a digitized 4 kHz low-pass analog signal with 8 bits per sample?

32 kHz Signup and view all the answers

What is the disadvantage of isochronous transmission in terms of error correction?

There is no error correction mechanism Signup and view all the answers

What is the purpose of a low pass filter in a PCM decoder?

To filter out high-frequency noise Signup and view all the answers

What is the advantage of isochronous transmission in terms of character transmission?

There is no need to pause between each character Signup and view all the answers

Study Notes

Transmission Modes

Data transmission can be accomplished in two modes: parallel and serial
In parallel mode, multiple bits are sent with each clock tick
In serial mode, 1 bit is sent with each clock tick
Serial transmission has three subclasses: asynchronous, synchronous, and isochronous

Parallel Transmission

Advantage: speed
Disadvantage: cost
Requires n communication lines (wires) to transmit the data stream
Limited to short distances due to high cost

Serial Transmission

Advantage: cost-effective
Reduces the cost of transmission over parallel by roughly a factor of n
Requires conversion devices at the interface between the sender and the line (parallel-to-serial) and between the line and the receiver (serial-to-parallel)

Asynchronous Transmission

Sends 1 start bit (0) at the beginning and 1 or more stop bits (1s) at the end of each byte
May have a gap between each byte
Efficiency calculation example: 20KB data transmission
Cheap and effective, suitable for low-speed communication, e.g., keyboard to computer connection

Synchronous Transmission

Bits are sent one after another without start or stop bits or gaps
Receiver groups the bits
Bits are usually sent as bytes, and many bytes are grouped in a frame
Frame is identified with a start and an end byte
Advantage: speed
Suitable for high-speed applications, e.g., transmission of data from one computer to another
Byte synchronization is accomplished in the data link layer
Efficiency calculation example: 20KB data transmission

Isochronous Transmission

Similar to synchronous transmission, but with almost zero time interval between blocks
Collects synchronous and asynchronous data from several devices within a time slot (125 micro-second)
Guarantees data arrival at a fixed rate
Suitable for real-time audio and video applications, e.g., TV images broadcast

Advantages and Disadvantages of Isochronous Transmission

Advantages: high transmission speed, no need to pause between each character, no start and stop bits required
Disadvantages: requires primary storage device at the sender station, no error correction, and relatively expensive

PCM Decoder

Recovers an analog signal from a digitized signal through:
- Hold circuit that holds the amplitude value of a pulse till the next pulse arrives
- Low-pass filter with a cutoff frequency equal to the highest frequency in the pre-sampled signal
The higher the value of L, the less distorted the recovered signal is

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Description

This quiz covers the concepts of digital transmission in data communications, including transmission modes and parallel/serial modes.

Data Communications Chapter 4: Digital Transmission

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