Serial and Parallel Transmission Quiz: Difference and Examples

Study Notes

Serial Communications

When communicating with a timesharing system over a modem, only a single channel is available, and bit-serial transmission is required.
In general, one channel will pass only one bit at a time.
Each bit represents a part of the message, and the individual bits are reassembled at the destination to compose the message.

Parity

There are four types of parity: even, odd, space, and mark.
Even parity: the total number of binary 1s must be an even number.
Odd parity: the total number of binary 1s must be an odd number.
Space parity: the parity bit will always be a binary zero (also known as bit filling).
Mark parity: the parity bit is always a binary 1 and acts only as a filler.
The parity bit is computed before the data is transmitted, and it depends on the initial parity of the data.

Error Detection and Correction

Parity is a reliable method of error detection, but it has limitations (e.g., if an even number of bits have been reversed, the parity will match even though an error has occurred).
Another approach to error detection involves the computation of a checksum.
If the sum of data plus checksum is nonzero, an error has occurred.
Errors may not only be detected but also corrected if additional code is added to a packet sequence.

Data Compression

Data compression involves assigning short binary codes to frequently used characters and longer codes to rarely used characters.
This procedure can result in a 50 percent or greater savings in the amount of data transmitted.
Data that represents images, for example, will usually compress significantly, perhaps by as much as 80 percent over its original size.
Data representing a computer program, on the other hand, may be reduced only by 15 or 20 percent.

Communication Media

IBM STP (shielded twisted pair) has a characteristic impedance.
Coaxial cable consists of two conductors: the inner conductor and the outer conductor, which is woven around it and provides a shield.
Optical fiber consists of thin glass fibers that can carry information at frequencies in the visible light spectrum and beyond.
The typical optical fiber consists of a very narrow strand of glass called the core, surrounded by a concentric layer of glass called the cladding, and a protective coating called the jacket.

Signal Transmission

QPSK (Quadrature Phase Shift Keying) is a modulation method used in Bell 212A-compatible modems and V.22.
QPSK employs shifting the phase of the carrier at a 600 baud rate plus an encoding technique.
Frames are used to transmit data, consisting of a group of binary digits, and can be individually checked at the receiving end.

Data Switching

Data switching is the transmission of data in a network, essentially switching or transmitting the data from one node to the next.
There are two modes of operation: half duplex, where both ends of the communication link can send and receive information but not at the same time, and simplex, where information can only be sent in one direction across the link.

Description

Test your knowledge on the differences between serial and parallel data transmission methods, such as the number of channels involved and the speed of communication. Understand how data is transferred between devices like microprocessors, memory chips, and timesharing systems.