transmission medium/ mediawireless transmission media 1. unguided transmission media : wireless,...

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Transmission Medium/ Media

The successful transmission of data depends principally on two factors: the quality of the signal being

transmitted and the characteristics of the transmission medium Transmission Medium (or Media) defined as Physical path that carry information between a sender to

a receiver. It’s key elements of data communication. Because choosing the appropriate media. Make effective and cost-effective of data communications. Medium or media of communication can be classify, into 2 major categories, as follows.

Classes of transmission media

1. Guided Transmission media : wires, fiber optics • Medium is important

2. Unguided Transmission media : wireless, radio transmission • Bandwidth produced by the antenna is more important


Design Factors for Transmission Media (Concerned with data rate and distance) 1. Transmission impairments: impairments, such as attenuation, limit the distance 2. Interference: overlapping frequency bands can distort or wipe out a signal 3. Number of receivers: more receivers introduces more attenuation 4. Bandwidth : higher bandwidth gives higher data rate (like a road)

1. Guided Transmission Media

• Twisted Pair Cable • Coaxial Cable • Fiber Optical Cable

1.1 Twisted Pair Cable The least expensive and most widely used guided transmission medium is twisted pair

If the pair of wires are not twisted, electromagnetic noises from, e.g., motors, will affect the closer wire more than the further one, thereby causing errors


Twisted pair is the least expensive and most widely used guided transmission medium. • Consists of two insulated copper wires arranged in a regular spiral pattern • The cable is an electrical cable, can transmit both analog and digital signal but twisted pair is also the

most common medium used for digital signaling • Least expensive and easy to install • Most commonly used in the telephone network and for communications within buildings • Requires amplifiers every 5-6 km for analog signals

Unshielded VS Shielded Twisted-Pair Cable


Unshielded Twisted-Pair (UTP) Shielded Twisted-Pair Cable (STP) - Suffers from external electromagnetic interference - Ordinary telephone wire - Cheapest - Easiest to install

- Has metal braid or sheathing that reduces interference

- Provides better performance at higher data rates

- More expensive - Harder to handle (thick, heavy)

Connector

2. Coaxial Cable


BNC connectors

Coaxial cable is widely used as a means of distributing TV signals to individual homes—cable TV used for long distance telephone transmission and LANs • Used to transmit both analog and digital signals • Superior frequency characteristics compared to twisted pair • Can support higher frequencies and data rates • Requires amplifiers every few kilometers for long distance transmission • Requires repeaters every few kilometers for digital transmission

3. Fiber Optical Cable


Fiber-optic cable connectors

Fiber optic cable is the transmission medium used to transmit data in the form of light.

Various glasses and plastics can be used to make optical fibers Widely used in long distance telecommunications Higher bandwidth No noise Performance, price and advantages have made it popular to use

Need Installation requires specialist because hard to install, easily broken and expensive

Guided transmission media summary

Type Advantage Disadvantage

Twisted Pair cable Very inexpensive Easy to install Already installed in many locations

Doesn’t pass high frequencies well

Coaxial cable Shielded Fairly inexpensive Moderately high bandwidth

Bulky and somewhat inflexible

Fiber optic cable Transmission unaffected by noise Very high bandwidth Great repeater spacing

Expensive to install


Wireless Transmission Media

1. Unguided Transmission media : wireless, radio transmission Unguided media transport electromagnetic waves without using a physical conductor. This type of

communication is often referred to as wireless communication. The mediums used in wireless communications are air, vacuum and even water. Air is the most

commonly used medium. Wireless Transmission Wireless transmission can be categorized into three broad groups:

• Radio waves • Microwaves • Infrared

THE DIFFERENCE BETWEEN RADIO WAVES AND MICROWAVES There is no clear difference between radio waves and microwaves.

- Electromagnetic waves ranging in frequencies between 3 KHz and 1 GHz are normally called radio waves.

- Waves ranging in frequencies between 1 and 300 GHz are normally called microwaves.

It is actually the behavior of the waves rather than the frequencies that determines the classification of wireless transmission.


Radio waves

Radio waves are normally omnidirectional. When an antenna transmits radio waves, they are propagated in all directions. This means that the sending and receiving antennas do not have to be aligned. The omnidirectional characteristics of radio waves make them useful for multicasting, in which there is one sender but many receivers. Our AM and FM radio stations, cordless phones and televisions are examples of multicasting.


The Disadvantage of Radio waves Radio waves transmitted by one antenna are susceptible to interference by another antenna that is

sending signals of the same frequency Bluetooth

Bluetooth technology is designed to serve as a new way of connecting it with the advantages of low investment, low energy consumption. There is a difference when compared to the communication with infrared light that can communicate through a barrier or wall and surround. Such as computers, printers, faxes and including PDAs.

Microwave


Electronic waves with frequencies between 1 GHz to 300 GHz are normally called microwaves. Unlike radio waves, microwaves are unidirectional, in which the sending and receiving antennas need to be aligned.

Microwaves propagation is line-of-sight therefore towers with mounted antennas need to be in direct sight of each other. Due to the unidirectional property of microwaves, a pair of antennas can be placed aligned together without interfering with another pair of antennas using the same frequency.

High-frequency microwaves cannot penetrate walls. This is why receiving antennas cannot be placed inside buildings. Infrared

Infrared is used in devices such as the mouse, wireless keyboard and printers. Some manufacturers provide a special port called the IrDA port that allows a wireless keyboard to communicate with a PC.

Infrared signals have frequencies between 300 GHz to 400 THz. They are used for short-range communication.

Infrared signals have high frequencies and cannot penetrate walls. Due to its short-range communication system, the use of an infrared communication system in one room will not be affected by the use of another system in the next room. This is why using an infrared TV remote control in our home will not interfere with the use of our neighbor’s infrared TV remote control.


THE DISADVANTAGES OF USING INFRARED Infrared signals cannot be used for long distance communication. In addition, we cannot use infrared

waves outside a building because sun's rays contain infrared waves that can interfere with communication. Satellite

Because microwave restrictions on the landscape that affect obscure wave. Thus, it has developed a satellite. A communication satellite is, In fact, Satellite is a microwave station. It is used to link two or more ground-based microwave transmitter/receivers, known as earth stations, or ground stations. Implementing such satellite to orbit above the Earth's surface, only three satellites, it can be cover to communicate to all the world. The satellite receives transmissions on one frequency band (uplink), amplifies or repeats the signal, and transmits it on another frequency (downlink).

WAP (Wireless Application Protocol) WAP is an international standard for wireless data communications by WAP protocol is active on

portable devices to use HTML to display it in the form of browser to be able surf to Internet.


Wi-Fi (Wireless Fidelity) Wi – Fi (Wireless Fidelity) is a standard that certifies that wireless devices (Wireless LAN) can work

together. And supports IEEE802.11b standard

Wi - Fi high-speed wireless Internet technology is commonly used in the world. Uses radio signals to transmit high speed data over the wireless network with the installation of the Access Point to connect to the device. Such as mobile phones, PDAs and notebook and so on.

WiMAX (Worldwide Interoperability for Microwave Access)

WiMAX is that the radius of 30 miles, or a distance of about 48, which means that WiMAX can provide coverage over a network, 3G mobile phones, up to 10 times more than that, it also has the speed. Data transmission of up to 75 megabits per second (Mbps), which is faster than 3G, up to 30 times faster than ever, and certainly with WiFi.

Factors to consider in choosing a communication medium. - Transmission Rate - The distance between the device must be connected - Cost - Easy to installation - Endure for environment - The method used in communications such as serial or parallel data transmission direction using a

simplex , half-duplex and full duplex.

transmission medium/ mediawireless transmission media 1. unguided transmission media : wireless,...

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