Data transmission
Data transmission, commonly referred to as digital transmission, involves the transfer of data between digital devices through various transmission media. It can be categorized into two primary modes: parallel transmission and serial transmission. In parallel transmission, multiple bits are sent simultaneously over separate data lines, making it a quick method for short distances. However, this method is costlier due to the required number of wires. In contrast, serial transmission sends bits one at a time over a single data line, which is more economical and suitable for longer distances, albeit slower.
Serial transmission can further be divided into asynchronous and synchronous types. Asynchronous transmission sends one byte at a time, using start and stop bits for synchronization, while synchronous transmission transmits longer frames of data without gaps, requiring precise timing between sender and receiver. Various transmission media, such as twisted pair cables, coaxial cables, fiber optic cables, and power line communication (PLC), are employed for data transfer. Each medium has unique properties and advantages, with fiber optic cables, for example, utilizing light to transmit data and offering high-speed capabilities. Understanding these concepts is essential for grasping the complexities of data transmission in modern technology.
On this Page
Data transmission
Data transmission, also known as digital transmission, is the transfer of data between digital devices through a transmission medium. Two different modes of data transmission exist: parallel transmission and serial transmission. Both modes transfer binary data, or binary bits. Parallel transmission uses data lines to send groups of bits simultaneously. In serial transmission, bits are sent one after the other. Serial transmission is either asynchronous or synchronous. Asynchronous transmission uses start bits and stop bits and also has gaps between the different bytes. With synchronous transmission, timing the transmission of each bit is required. Different transmission media is used to transfer data.
Overview
In both parallel transmission and serial transmission bits are represented by series of 0s and 1s. In parallel transmission, the bits of data are grouped together in a certain length and are sent from the sender to the receiver. Data lines, or wires, connect the sender and receiver. Each data line sends one group of bits, and all of the bits are sent where they need to go at once. This means that all of the groups of bits are sent simultaneously on separate data lines. Typically used for short distances, parallel transmission is useful because it is a quick way of transferring data all at once. However, this type of data transmission is expensive because of the large number of wires that are required.
Serial transmission differs from parallel transmission because bits are sent serially, or one after the other. Unlike parallel transmission, only one data line is needed between the sender and receiver. Therefore, all of the bits are sent on the same line. Serial transmission is typically used over long distances and is less expensive than parallel transmission because only one line is needed. However, serial transmission is slower than parallel transmission because the bits are transmitted one at a time.
Asynchronous transmission and synchronous transmission involve bit synchronization, which determines the beginning and end of the data transmission and offers timing control. With asynchronous transmission, one byte of data (either a number or a letter of the alphabet) is sent at a time. This type of serial transmission uses start bits and stop bits. A start bit, usually a 0, tells the receiver that a new group of bits has arrived, while a stop bit, usually a 1, indicates that transmission has ended. Gaps, or idle time, exist between the transmission of different bytes.
With synchronous transmission, the bit stream consists of longer frames of multiple bytes. In synchronous transmission no start or stop bits or gaps exist between the different bytes. Therefore, timing the transmission of each bit is required. Both the sender and receiver must operate at the same clock frequency, and the receiver must recognize and separate the bit stream into bytes to reconstruct the original information. Synchronous transmission is faster and more efficient than asynchronous transmission, mainly because of the absence of the extra start and stop bits and gaps. Asynchronous transmission is less expensive than synchronous transmission.
Data is transferred through transmission media, including magnetic media, twisted pair cables, coaxial cables, fiber optic cables, and power line communication (PLC). Magnetic media uses either magnetic tapes or magnetic discs. Data backup is stored on the tapes or discs and then physically transferred. Magnetic media typically is used when the size of data is very large.
A twisted pair cable consists of two insulated copper wires that are twisted together. One of the wires carries the signal, and the other wire usually serves as a ground, which is a reference point that directs spikes in electricity away from the cable. The reason the wires are twisted together is to reduce noise, which is electromagnetic interference, and cross talk, which is unwanted signals in the channel. Twisted pair cables come in two types: shielded twisted pair (STP) cable and unshielded twisted pair (UTP). The STP cable is covered in metal foil, while the UTP cable is not. STP cables are less susceptible to noise and cross talk than UTP cables.
The coaxial cable consists of two copper wires. The core wire is covered in an insulating sheath. The other wire is wrapped around the core wire and is also covered by a sheath. Both wires are enclosed in a plastic cover. Coaxial cables offer protection against noise and cross talk. They come in three categories—RG-59 for cable television, RG-58 for thin Ethernet, which is a thin, flexible coaxial cable, and RG-11 for thick Ethernet, which is a thicker, less flexible cable than the thin Ethernet.
A fiber optic cable uses the properties of light. It has a core made of glass or plastic. Light is emitted at one end of the wire, travels through the wire, and is converted into electric data at the other end. Fiber optic cables are available in two modes: single mode fiber and multimode fiber. As their names imply, single mode fiber carries one ray of light, while multimode fiber carries multiple rays of light.
Power line communication (PLC) transmits data signals over power cables. PLC modulates the data and sends it over the cables, and then the receiver demodulates the data and interprets it. PLC can control and monitor powered devices. Narrow band PLC and broadband PLC are two types of PLC. Broadband PLC offers higher data rates than narrow band PLC.
Bibliography
“Cross Talk.” Merriam-Webster. Merriam-Webster, Incorporated. Web. 10 Nov. 2014. http://www.merriam-webster.com/dictionary/crosstalk
“Digital Transmission.” Tutorialspoint. Tutorialspoint. Web. 10 Nov. 2014. http://www.tutorialspoint.com/data‗communication‗computer‗network/digital‗transmission.htm
Thakur, Dinesh. “Ethernet Cables - What Is an Ethernet Cable?” E Computer Notes. E Computer Notes. Web. 12 Nov. 2014. http://ecomputernotes.com/computernetworkingnotes/communication-networks/ethernet-cables-in-computer-networking
Thakur, Dinesh. “What Is Data Transmission? Types of Data Transmission.” E Computer Notes. E Computer Notes. Web. 10 Nov. 2014. http://ecomputernotes.com/computernetworkingnotes/communication-networks/data-transmission
“Transmission Media.” Tutorialspoint. Tutorialspoint. Web. 10 Nov. 2014. http://www.tutorialspoint.com/data‗communication‗computer‗network/transmission‗media.htm
“What Is an Electrical Ground?” wiseGEEK. wiseGEEK. Web. 12 Nov. 2014. http://www.wisegeek.org/what-is-an-electrical-ground.htm