Assalamualaikum. I got an assignment for my ict subject to create a blog and publish information about ict.
Before that, i want to introduce myself. My name is Muhammad Khairi bin Mohd Alim. I am a student from SMK Tun Habab. I am from 6 Rendah Al-Farabi. I live at Felda Air Tawar 1, Kota Tinggi, Johor. This is my first blog. I hope you enjoy reading my articles.
What is transmission media?
Transmission media is a pathway that carries the information from sender to receiver.We use different types of cables or waves to transmit data. Data is transmitted normally through electrical or electromagnetic signals.
What are the types of transmission media.
Transmission media are divided into two groups.
1. Wired or Guided Media or Bound Transmission Media
2. Wireless or Unguided Media or Unbound Transmission Media
Wired or Guided Media or Bound Transmission Media: Bound transmission media are the cables that are tangible or have physical existence and are limited by the physical geography. Popular bound transmission media in use are twisted pair cable, co-axial cable and fiber optical cable. Each of them has its own characteristics like transmission speed, effect of noise, physical appearance, cost etc.
Wireless or Unguided Media or Unbound Transmission Media: Unbound transmission media are the ways of transmitting data without using any cables. These media are not bounded by physical geography. This type of transmission is called Wireless communication. Nowadays wireless communication is becoming popular. Wireless LANs are being installed in office and college campuses. This transmission uses Microwave, Radio wave, Infra red are some of popular unbound transmission media.
COMPUTER NETWORK
A computer network is a group of computers connected to each other electronically. This means that the computers can "talk" to each other and that every computer in the network can send information to the others. Usually, this means that the speed of the connection is fast - faster than a normal connection to the Internet. Some basic types of computer networks include:
- A local area network (often called a LAN) connects two or more computers, and may be called a corporate network in an office or business setting.
- An "internetwork", sometimes called a Wide Area Network (because of the wide distance between networks) connects two or more smaller networks together. The largest internetwork is called the Internet.
Computers can be part of several different networks. Networks can also be parts of bigger networks. The local area network in a small business is usually connected to the corporate network of the larger company. Any connected machine at any level of the organization may be able to access the Internet, for example to demonstrate computers in the store, display its catalogue through a web server, or convert received orders into shipping instructions.
Microsoft Windows, Linux and most other operating systems use TCP/IP for networking. Apple Macintosh computers used Appletalk in the past, but it uses TCP/IP now.
To set up a network an appropriate media is required. This can be wired or wireless. Twisted-pair, co-axial or fiber-optic are examples of cable and infra-red, blue-tooth, radio-wave, micro-wave etc. are wireless media used for networking. When you are working with a mere LAN, computers, media and peripherals are sufficient. But when you are working with a wider range you have use some additional devices like bridge, gateway or router to connect different small or large networks. And obviously a protocol must be maintained.
To set up a network you have to select an appropriate topology to arrange the hardware devices using the media. Topologies generally used are bus-topology, ring-topology, star-topology, tree-topology, object-oriented topology etc. Among these star-topology and tree-topology are most popular nowadays.
Wired
In computing terminology, the term "wired" is used to differentiate between wireless connections and those that involve cables. While wireless devices communicate over the air, a wired setup uses physical cables to transfer data between different devices and computer systems.
A wired network is a common type of wired configuration. Most wired networks use Ethernet cables to transfer data between connected PCs. In a small wired network, a single router may be used to connect all the computers. Larger networks often involve multiple routers or switches that connect to each other. One of these devices typically connects to a cable modem, T1 line, or other type of Internet connection that provides Internet access to all devices connected to the network.
Wired may refer to peripheral devices as well. Since many keyboards and mice are now wireless, "wired" is often used to describe input devices that connect to a USB port. Peripherals such as monitors and external hard drives also use cables, but they are rarely called wired devices since wireless options are generally not available.
While many peripherals are now wireless, some users still prefer wired devices, since they have a few benefits over their wireless counterparts. For example, an Ethernet connection is not prone to signal interference that can slow down Wi-Fi connections. Additionally, wired network connections are generally faster than wireless ones, which allows for faster data transfer rates. Some users also prefer wired peripherals since their is no need to replace batteries on a regular basis. Gamers especially prefer wireless keyboards and mice since they have lower latency and can be backlit, thanks to the power provided by the USB connection.
A wired network is a common type of wired configuration. Most wired networks use Ethernet cables to transfer data between connected PCs. In a small wired network, a single router may be used to connect all the computers. Larger networks often involve multiple routers or switches that connect to each other. One of these devices typically connects to a cable modem, T1 line, or other type of Internet connection that provides Internet access to all devices connected to the network.
Wired may refer to peripheral devices as well. Since many keyboards and mice are now wireless, "wired" is often used to describe input devices that connect to a USB port. Peripherals such as monitors and external hard drives also use cables, but they are rarely called wired devices since wireless options are generally not available.
While many peripherals are now wireless, some users still prefer wired devices, since they have a few benefits over their wireless counterparts. For example, an Ethernet connection is not prone to signal interference that can slow down Wi-Fi connections. Additionally, wired network connections are generally faster than wireless ones, which allows for faster data transfer rates. Some users also prefer wired peripherals since their is no need to replace batteries on a regular basis. Gamers especially prefer wireless keyboards and mice since they have lower latency and can be backlit, thanks to the power provided by the USB connection.
Twisted Pair Cable
A twisted pair cable is made of two plastic insulated copper wires twisted together to form a single media. Out of these two wires only one carries actual signal and another is used for ground reference. The twists between wires is helpful in reducing noise (electro-magnetic interference) and crosstalk.
There are two types of twisted pair cables available:
- Shielded Twisted Pair (STP) Cable
- Unshielded Twisted Pair (UTP) Cable
STP cables comes with twisted wire pair covered in metal foil. This makes it more indifferent to noise and crosstalk.
UTP has seven categories, each suitable for specific use. In computer networks, Cat-5, Cat-5e and Cat-6 cables are mostly used. UTP cables are connected by RJ45 connectors.
Coaxial Cable
Coaxial cables has two wires of copper. The core wire lies in center and is made of solid conductor. Core is enclosed in an insulating sheath. Over the sheath the second wire is wrapped around and that too in turn encased by insulator sheath. This all is covered by plastic cover.
Because of its structure coax cables are capable of carrying high frequency signals than that of twisted pair cables. The wrapped structure provides it a good shield against noise and cross talk. Coaxial cables provide high bandwidth rates of up to 450 mbps.
There are three categories of Coax cables namely, RG-59 (Cable TV), RG-58 (Thin Ethernet) and RG-11 (Thick Ethernet. RG stands for Radio Government.
Cables are connected using BNC connector and BNC-T. BNC terminator is used to terminate the wire at the far ends.
Power Lines
Power Line communication is Layer-1 (Physical Layer) technology which uses power cables to transmit data signals. Send in PLC modulates data and sent over the cables. The receiver on the other end de-modulates the data and interprets.
Because power lines are widely deployed, PLC can make all powered devices controlled and monitored. PLC works in half-duplex.
Two types of PLC exists:
-Narrow band PLC
-Broad band PLC
Narrow band PLC provides lower data rates up to 100s of kbps, as they work at lower frequencies (3-5000 kHz). But can be spread over several kilometers.
Broadband PLC provides higher data rates up to 100s of Mbps and works at higher frequencies (1.8 – 250 MHz). But cannot be much extended as Narrowband PLC.
Fiber Optics
Fiber Optic works on the properties of light. When light ray hits at critical angle it tends to refracts at 90 degree. This property has been used in fiber optic. The core of fiber optic cable is made of high quality glass or plastic. From one end of it light is emitted, it travels through it and at the other end light detector detects light stream and converts it to electric data form.
Fiber Optic provides the highest mode of speed. It comes in two modes, one is single mode fiber and second is multimode fiber. Single mode fiber can carries single ray of light whereas multimode is capable of carrying multiple beams of light.
Fiber Optic also comes in unidirectional and bidirectional capabilities. To connect and access Fiber Optic special type of connectors are used. These can be SC (Subscriber Channel), ST (Straight Tip) or MT-RJ.
wireless
Wireless communication is the transfer of information between two or more points that are not connected by an electrical conductor.
The most common wireless technologies use radio. With radio waves distances can be short, such as a few meters for television or as far as thousands or even millions of kilometers for deep-space radio communications. It encompasses various types of fixed, mobile, and portable applications, including two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of applications of radio wireless technology include GPS units, garage door openers, wireless computer mice, keyboards andheadsets, headphones, radio receivers, satellite television, broadcast television and cordless telephones.
Somewhat less common methods of achieving wireless communications includes the use of other electromagnetic wireless technologies, such as light, magnetic, or electric fields or the use of sound.
A communications satellite or comsat is an artificial satellite sent to space for the purpose of telecommunications. Modern communications satellites use a variety of orbits including geostationary orbits, Molniya orbits, elliptical orbits and low (polar and non-polar)Earth orbits.
For fixed (point-to-point) services, communications satellites provide a microwave radio relay technology complementary to that of communication cables. They are also used for mobile applications such as communications to ships, vehicles, planes and hand-held terminals, and for TV and radio broadcasting.
Bluetooth
Bluetooth is a wireless technology standard for exchanging data over short distances (using short-wavelength UHF radio waves in the ISM band from 2.4 to 2.485 GHz[2]) from fixed and mobile devices, and building personal area networks (PANs). Invented by telecom vendor Ericsson in 1994,[3] it was originally conceived as a wireless alternative to RS-232 data cables. It can connect several devices, overcoming problems of synchronization.
Microwave
Microwave transmission refers to the technology of transmitting information or energy by the use of radio waves whose wavelengths are conveniently measured in small numbers of centimetre; these are called microwaves. This part of the radio spectrum ranges acrossfrequencies of roughly 1.0 gigahertz (GHz) to 30 GHz. These correspond to wavelengths from 30 centimeters down to 1.0 cm.
Infrared
Infrared (IR) is electromagnetic radiation with longer wavelengths than those of visible light, extending from the nominal red edge of thevisible spectrum at 700 nanometers (nm) to 1 mm. This range of wavelengths corresponds to a frequency range of approximately 430 THzdown to 300 GHz.[1] Most of the thermal radiation emitted by objects near room temperature is infrared.
Communication protocols
In telecommunications, a communications protocol is a system of digital rules for data exchange within or between computers.
- Definition of Protocol Control Information (PCI) format which forms the PDU header
- Definition of procedures for transmitting and receiving PDUs
- Definition of services provided by the protocol layers
A Protocol Data Unit
The PDUs exchanged have two parts: a header (also known as the Protocol Control Information (PCI)) and a payload (also known as a Service Data Unit (SDU)). The protocol does not define or constrain the data carried in the payload part. It does specify the format of the PCI, defining the fields which are present and the way in which the patterns of bits are to be interpreted.A protocol also defines the procedures which determine how the PDU will be processed at the transmit and receive nodes. The procedures specify the valid values for the PCI fields, and the action be taken upon reception of each PCI value (usually based on stored control information). Examples of procedures which are implemented in protocols include:
- error recovery (e.g. the checkpoint procedure, the go-back-n procedure)
- flow control
- segmentation
- service access point selection
- connection management
A protocol implemented by several processes (represented by circles) communicating using queues of PDUs, a shared information area (shown as a rectangle) and function calls between the processes (represented by arrows)
Protocols are usually implemented by writing a number of programs (processes) which communicate with one another through queues and by function calls. One or more timers are also usually required to ensure correct operation of the protocol. To start and stop timers, a protocol normally uses an interface to the computer's operating system. This interface is also used to request new (empty) buffers for received PDUs (or PDUs created by the layer) and to release buffers which are no longer needed by the protocol.Protocols are generally described using a layered architecture known as the OSI reference model. Which abstracts the details of the protocol and allows a simple description of the service provided by the protocol to the protocol layer above and the service required by protocol layer from the layer below.
Examples of protocols include:
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