There are several common terminologies used for signal rate in the literature of computer networks. Which of the following is not a common terminology for signal rate ?

Question

Accepted Answer

The correct option is (3):
Bit rate, or the number of bits transmitted per second (bits/s), is fundamentally a measure of the **data transmission rate**, which represents the volume of digital information moved. The term **signal rate** refers to the rate at which the signal elements or waveforms change on the transmission medium, formally known as the **symbol rate** or **baud rate**. In complex modulation schemes, a single signal element (symbol) can encode multiple data bits. Because of this separation—where Bit rate measures the speed of data and Baud rate measures the speed of the signal change—Bit rate is considered a measure of data throughput, and thus it is not a common terminology used to define the signal's physical change rate itself.

The incorrect option is (1):
**Pulse rate** is a terminology that is frequently and correctly used, especially in the context of digital baseband transmission, where the individual signal elements are transmitted as electrical 'pulses'. The rate at which these signal pulses are sent across the medium is, therefore, the pulse rate. It serves as a direct synonym for the symbol rate or signal rate in this type of digital communication.

The incorrect option is (2):
**Modulation rate** is an explicit synonym for the symbol rate or signal rate. In any modulated transmission system, the modulation rate is the number of times per second that the carrier signal's characteristics (like its amplitude, frequency, or phase) are altered to encode data. It directly quantifies the frequency of the signaling events on the physical channel.

The incorrect option is (4):
**Baud rate** is a classic and widely accepted terminology for the signal rate in the field of data communications. It is the unit of measure (Baud, or symbols per second) that directly specifies the number of distinct signal elements, or symbols, transmitted over the physical medium in one second. It is the standard technical term for the signal change rate.