## Introduction

Data transfer rate refers to the number of data transmitted by the data path within the unit time. It typically includes three contents:

1. Data signal rate, indicating the number of bits that transmit data information within a second, and the unit is bit / second (b / s).

2. Modulation rate, the modulation rate reflects the frequency of signal waveform transformation, which is defined as the number of transmitted signal symbols (waveforms) per second, also known as symbol rate, symbol rate or baud rate. The unit is BAUD.

3. Data transfer rate, indicating the average of the bit, character, or information group between the two corresponding devices between the two corresponding devices in the data transmission system. Its unit can be bits, characters, or information groups / seconds, minutes or hours, the corresponding device refers to the modem, an intermediate device, or a data source. Transmission rates can be applied to different functions. The reaction time can help network administrators find what location rate declines and potential blocking in the network. By analyzing the data transfer rate, adjustment, as a protective measures, the system can run more efficient and can prevent special bandwidth limitations when high loads. Test equipment such as fiber optic loop testing can help measure and manage data transmission rates.

## Other Interpretation

Data Transfer Rate is also a "multiplier" number that people often say. When a single transmission, 150KB data can be transmitted each second; 600KB data can be transmitted per second; when 40 times speed transmission, 6MB data can be transmitted per second (the Internet data transmission rate is up to 10Mbps) ..... Push it in this class. The discussion in the market is mostly 40 times the speed to 50 times. However, pay attention to the actual use, the above rate will be greatly reduced by the optical disk read speed and the CPU transmission itself, and the higher the speed, the greater the discount. Typically, the average transmission rate can reach 3 to 4MB.

The data transfer rate is the number of transmitted data symbols within the unit time. It is a major indicator for measuring system transmission capabilities, which usually uses the following different definitions:

The data transfer rate is the number of binary symbols per second, also known as bit rate. The unit is bits / second (bit / s).

The modulation rate is a number of transmitted signal symbols per second, also known as the baud rate, and the unit is BD).

Data transfer rate is a bit, character, or code group average transmitted between the corresponding devices in the data transmission system in unit time. In this definition, the corresponding device often refers to the modem, an intermediate device, or a data source and data. The unit is bit / sec (bit / s), characters / second or code group / second.

It should be noted that the difference between bits and baud. Bit (BIT) is an abbreviation of binary digit, one bit is a binary code "0" or "1". Bit is also the unit of information, which is defined as: in a binary sequence, "1" and "0" appearance probability is equal, and the front and rear symbols are independent, and the amount of information of each binary code element is 1 bit. Potter is a metric unit associated with signal waveform changes. Therefore, the data communication rate and the modulation rate are two different concepts. In cases only in binary, 1 baud is equal to 1 bit / sec, ie the data communication rate and the modulation rate are equal to the value. When the signal symbol is M., the amount of information loaded by each symbol is

Data transfer rate is different from the data transmission rate. The data transmission rate is the rate of transmitting data, and the data transfer rate is the average data transfer rate actually reached. It is not only related to the number of bits sent, but also related to the error control, communication procedures, and channel error rates, that is, related to transmission efficiency. Therefore, the data transfer rate is always less than the data signaling rate.

## Computational

Common data transfer rate units are: Kbps, Mbps, Gbps and TB / S, the fastest Ethernet area network theoretical transmission rate (that is, "bandwidth" 10Gbit / s. Where:

1kbps = 1024 bps

1Mbps = 1024 * 1024bps

1Gbps = 1024 * 1024 * 1024bps

1tbps = 1024 * 1024 * 1024 * 1024bps

Data transfer rate calculation formula:

r = (1 / t) * log₂n (bps)

where: t is a number Width (full wide code) or repetition period (zeroing code) of the pulse signal, the unit is second; a digital pulse is also referred to as a symbol, n is a valid discrete value taken by a symbol, also called modulating electrical Flat numbers, n generally take 2 integer times. If a symbol can take 0 and 1 discrete value, the symbol can only carry one (bit) binary information; if a symbol can take 100, 01, 10, 11 discrete values, the symbol is Can carry two binary information. In this class, if a symbol can take N type discrete value, the symbol can carry LOG ₂n bit binary information. When n = 2, the formula of the data transmission rate can be simplified to: r = 1 / t, indicating the repetition frequency of the data transmission equal to the symbol pulse. Thereby, another technical indicator-signal transmission rate, also known as the element rate, the modulation rate or the baud rate (in units of baud, is recorded as a BAUD). The signal transmission rate represents the number of symbols transmitted through the channel within the unit time, that is, the signal is modulated. If the amount of information contained in each symbol is 1 bit, the baud rate is equal to the bit rate. Calculate formula: b = 1 / t (baud), in the formula T is the width of the signal symbol, in seconds.

It can be obtained from the above two formulas: r = b log₂n (bit / s), or b = r / log₂n (baud)

In the computer, a symbolic meaning is The high and low level represents the logic "1" and logic "0", so the amount of information contained in each symbol is just 1 bit, so in computer communication, + often referred to as "baud rate" , Ie:

1 baud (b) = 1 bit (bit) = 1 bits / sec (1bit / s)

, for example: the fastest transmission rate of electrical typewriters is per Second 10 characters per second, each character contains 11 binary bits, then the data transfer rate is: 11-bit / character × 10 characters / second = 110 bits / second = 110 baud.

There is also a method of data transmission rate is "bit time" (TD), which refers to the time required for transmitting a binary bit, represented by TD. The computer formula is as follows.

td = 1 / baud rate = 1 / b

, for example: b = 110bit / s, then td = 1/110 ≈ 0.0091S (9.1ms)

## Data Transfer

Data transfer, digital transmission, or digital communication is data (digital bitstream) physical transmission pipe for multi-point communication in a point-to-point or point-to-multipoint communication. Such pipes include twisted pairs, fibers, wireless communication channels, storage devices, and computer bus. The data itself represents an electromagnetic signal, such as voltage, radio waves, microwave or infrared signals.

Analog communication is used to transmit continuously changing analog signals, and digital communication is used to transmit discrete messages. Using a digital modulation method, the discrete message can be expressed as a series of pulses through a line code (baseband transmission), or a set of limited continuous variation waveforms (passband transmission). Passband modulation and corresponding demodulation (also known as detection) is implemented by modem devices. In accordance with the most common definition of the digital signal, the bit stream typically expressed in two signals of the baseband and the passband is considered to be data transmission. In another definition, only the baseband signal is considered, and the passband transmission of the data is considered as a form of digital mode conversion.

Data Transmission can be digital information originating from the data source, such as a computer or a keyboard. It is also possible to digit a analog signal such as a telephone or video signal to a bit stream, such as using a pulse coded modulation (PCM) or a further data compression (digital mode conversion and data compression) scheme. The codec of this source is made by the codec device.