unit 8 communication technology

BTEC NATIONAL (CERT) FOT ICT PRACTITIONERS UNIT 8

Communication Technology

Task 1 – Signal Theory

Byte – byte is a term used for the unit which computer storage is measured in, 1 byte consists of 8 bits, a kilobyte (or 1 KB) consists of 1024 bytes. A megabyte (1 MB) consists of 1024 KB. A gigabyte consists of 1024 MB.

Synchronous & Asynchronous Data Transmission – these are two ways which are used to regulate the sending of data. Like always for more than one device to communicate there must be a signal which synchronises the transmission on receipt of data which is called the clocking signal. So when both devices send and receive suing the same clock signal, they communicate and transfer data accurately. The second device asynchronous is used to refer systems to communicate one way on demand as it is without clocking such as a computer to a printer.

Task 2 – Methods of Communication & Protocols

Simplex – this is when communication is only one way, for example from a computer to a printer, as the printer doesn’t send data back to the computer this is known as simplex and it is only in need of one serial lane.

Half Duplex –this is when two devices can communicate through the same lane but not at the same time, for example when a computer is sending data to the USB drive then at that moment of transmission the USB drive can not send anything back until the transmission from the computer is finished.

Duplex –this is when communication can take place from both ends at the same time, so in other words, you can send and receive at the same time, for example, mobile phones, when you call someone, both callers can speak at the same time.

USB –the USB is a means of communication when plugged in the computer, it’s a way to save data onto the USB, or there are other resources that use USB for example, wireless internet on a laptop, when you connect the USB which you got from the service provider and you plug it in, once plugged in you are connected to the internet, USB is also used for other resources, such as connecting mobile phones to computer and also connecting digital cameras, etc.

Task 3 – Communication Protocols

Wi-Fi –

Allows users to connect with their pc or laptop without the need of being wired into a socket
Creates portable network centers which can be taken anywhere on the globe
Serves to enhance the range of the network so that a connection could be made from those unreachable places where it may be too expensive to run cables
Narrowband sends a signal over a frequency range which is limited
Spread spectrum uses range of techniques & frequencies
802.11 and 802.11a operates at speeds of up to 6mbits per second
802.11b operates at a speed of 11mbits per second and is commonly used for wireless networking at school, home, office or a small business
802.11g is similar to the range of Bluetooth but with more power as it can work at a speed up to 54mbits per second, and operates in the 2.4GHz

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Bluetooth –

Ratified as
Added support for non-encrypted channels.
Received Signal Strength Indicator ().
Extended inquiry response
Bluetooth Radio
Higher transmission speeds in practice, up to 721kbit/s, as in 1.1.
Extended Synchronous Connections (eSCO), which improve voice quality of audio links by allowing retransmissions of corrupted packets, and may optionally increase audio latency to provide better support for concurrent data transfer.

GSM –

Devices connect by searching
Operates I the 900 or 1800mhz bands
The transmission power in a handset is limited to ...

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Bluetooth –

Ratified as
Added support for non-encrypted channels.
Received Signal Strength Indicator ().
Extended inquiry response
Bluetooth Radio
Higher transmission speeds in practice, up to 721kbit/s, as in 1.1.
Extended Synchronous Connections (eSCO), which improve voice quality of audio links by allowing retransmissions of corrupted packets, and may optionally increase audio latency to provide better support for concurrent data transfer.

GSM –

Devices connect by searching
Operates I the 900 or 1800mhz bands
The transmission power in a handset is limited to 1 watt
Indoor coverage
Sends synchronous and asynchronous data.
The data rates that are supported by GSM are are 300 bps, 600 bps, 1200 bps, 2400 bps, and 9600 bps
Lets you send short messages known as SMS
Enhance voice calling quality
Cheaper calls

Task 4 - Transmission Media

Coaxial – this is a device which is used to connect telecommunication devices which use high-frequency and broadband connections. This is a cable which has four components listed below:

Copper Core
Outer Plastic Sheath
Braided Copper Shielding
White Polythene Inner Insulator (dielectric)

On this cable the braided copper shield surrounds the insulator, this shield which is known also as a screen blocks electromagnetic interference. This cable is commonly used to carry radio frequencies and television signals as it has a much greater capacity than a standard copper wire. There are different types of coaxial cable, such as the thin Ethernet (10 base 2) which is used for networking at 10Mbps up to about 200 meters, and also the thick Ethernet and the amateur (ham) radio. The thick Ethernet (10 base 5) is used as the thin Ethernet but the distance is at 500 meters.

Optical Fibre – this is a device that uses light for data transferring. The most commonly used optical fibre is the semi-conductor such as light emitting diode and laser diode. LEDs or Laser generate small pulses and then send them down the fibre which is a small thin stick of glass. At the other end the Photodiodes detect the small pulses. This device works at very high speeds, up into gigabytes.

This device is capable of sustaining high transmission rates which is why it is used for broadband applications such as music, video and voice. Unlike copper, this device is not affected by stray electromagnetic interference and can be manufactured into single mode and multimode, single mode is used for long distances up to 3km carrying a single beam of light and the multimode is used for short distances up to 2km carrying multiple numbers of light beams which means more data.

UTP & STP – these two stand for unshielded and shielded twisted pair which uses copper wires. The core of both of these is copper therefore this is a really good conductor and also is easy to work with. In both cables, the single wires are twisted to cut out crosstalk which is when they intermingle with each other. The STP cable has a shield round it which is a metallic coated plastic foil and is within the plastic sheath that is used block electromagnetic interference. These two devices work at 10 gigabytes and are used for network connection, to send and receive data. As UTP has no shield it is vulnerable to radio frequency and electromagnetic interference.

Infrared – this device is used to wirelessly connect the phone to other devices such as other phones or the internet to send and receive data. This device can connect the phone to a computer, so that the computer can use the phone to make a data connection to the Internet. Infrared is an energy similar to visible light but with a longer wavelength. Infrared energy is cannot be seen by the human eye, infrared energy is emitted by all objects at ordinary temperatures. Its speed is from 1 to 152 M-bits per second.

Radio Waves - Radio waves are electromagnetic waves occurring on the radio frequency portion of the electromagnetic spectrum. It is commonly used to send data to radios, TVs and telephones. As radio waves are a part of the Electromagnetic Spectrum, the waves of the electromagnetic spectrum travel at the same speed of 300,000kms per second in space.

Task 5 – Role of Network Components

Hubs – A network hub is a device for connecting multiple Ethernet devices together, making a single network segment.

All the connections in a hub repeat the incoming signal to all the outgoing ports and is used to connect the cables that connect to a termination point at a users location.

Switches – The main function of a switch is to increase speed of communications in a network. It creates virtual circuits between each device communicating on the system which boosts its bandwidth, security and reduces collisions.

They can be used in LAN to control large systems which require a core to control the other switches on the system. Network switches can be used in Local Area Network to increase the speed of the connection.

Routers – It is a device used to connect a network to the internet. Routers connect two or more logical subnets. When routers are combined with other systems, routers provide access control and firewalls and control connections between different sections of a company LAN.

Routers operate in two different planes, control plane in which the router designates the interface which is most appropriate for forwarding specific packets to their destination and forwarding plane, which confronts the process of sending a packet received on a logical interface to an outbound logical interface.

Repeaters – A repeater is an electromechanical device used to regenerate telegraph signals. A repeater is used to extend the reach of a network cable beyond the normal range.

Repeaters can be used in radio communication services and these particular types often transmit and receive on different frequencies. A special subgroup of those repeaters is those used in amateur radio.

Bridges – A network Bridge makes it easy to connect LAN segments.

Bridges reduce the amount of traffic on a LAN by dividing it into two segments. A bridge inspects incoming traffic, it then decides whether to forward or discard it.

Gateways – A gateway is a network point which acts as an entrance to another network.

The main function of a gateway is to convert protocols among communication networks. A gateway can be used as a firewall or proxy server and a firewall server for network enterprise.

Wireless Device – This is a device that connects and compromises different communication devices to form a wireless network.

A wireless network lets you go wherever you are using the same internet access. Wireless Access Points can be used to boost a wireless signal across a building to ensure network coverage.

Task 6 – Types of Communication Devices

DTE – this is short for Data Terminal Equipment, DTE is a computer or communication device that generates or is the final destination of data. A device that is labeled as a DTE device is a device that all the EIA232 standards and is commonly the computer or the terminal

DCE – this is short for Data Circuit-Terminating Equipment, DCE is a device such as dial-up modems that establish and control the data link via the telephone network.

How DTE & DCE Work – first of all DCE devices provide the clock signal which is the internal clocking and the DTE device synchronizes on the provided clock which is the external clocking. DTE is known as the male connector and DCE is known as the female connector. Commonly the DTE device is the terminal/computer and the DCE is the modem. When you connect both devices without a modem or a similar translator between then a null modem must be used. DTE transmits on pin connector number 2 (p2) and receives on pin connector number 3 (p3), however the DCE is the opposite as it receives on p3 and transmits on p2.

3G Mobile Phone – this is the next generation of wireless connection. Its goal is to have wireless connection on the mobile phone from anywhere and also with a high-speed connection of up to 2megabits per second. Using 3G you can have access to your Emails, also file transfers, video calling and full use of the Internet in its proper form. A lot of mobile brands are creating mobile phone devices with 3G built in, so an individual will be able to stay connected wherever he goes.

How Does 3G Work – 3G stands for Geographical cells and has a hierarchal network of numerous sized cells.

These are:

Marco Cell – this is the biggest cell of all three areas, it covers normally around the size of a whole city
Micro Cell – this cell covers an area about the size of a city center
Pico Cell – this is the smallest cell from all three, this only covers either a office, hotel or airport, this is also known as a hot spot

The reason behind these cells are basically because shorter distance communications are faster and allow more users to use therefore this is used in offices etc.

For example, a Nokia 6630 has 3G built in and below is the specifications.