Information Processes & Technology:

Communication SystemsCharacteristics of Communication Systems

A communication system allows its users to send and receive data and information The framework in which communication systems function is shown in the diagram below,

where it represents Skype/MSN as a communication system.

Functions performed within communication systems to send a message: Message creation Organisation of packets at the interface between source and transmitter Signal generation by the transmitter Transmission via a medium Synchronising the exchange Addressing and routing Error detection and correction Security and management

Protocols in communication: A protocol is a set of rules that governs a communication process ‘Handshaking’ is the process of establishing a communication link and agreeing on which

protocol to use A communications protocol must define the following:

o Rate of transmission (in baud or bps)o Whether transmission is to be synchronous or asynchronouso Whether data is to be transmitted in half-duplex or full-duplex mode

Also, protocols can include sophisticated techniques for detecting and recovering from transmission errors and for encoding and decoding data.

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Ethernet Cable Wireless

Network Interface

Card

Common protocols: TCP/IP: Transmission Control Protocol/Internet Protocol – rules that split data into packets

for transfer across the internet HTTP: Hyper Text Transfer Protocol – allow the displaying of files containing hypertext links

across a network FTP: File Transfer Protocol – the protocol defining the transfer of files over a network or the

internet SMTP: Simple Mail Transfer Protocol – sending of e-mail messages POP: Post Office Protocol – retrieves e-mail messages

SSL : Secure Sockets Layer – used for encryption of data for secure data transmission

The client-server architecture:

The client controls the user interface and application The server controls access to the network Thin clients:

o A thin client is designed to be especially small so that the bulk of the data processing occurs on the server; a thin client is a network computer without a hard disk drive.

o Thin clients can be found in medical offices, airline ticketing, schools, etc.o Easy to install, lower total costs than fat clients

Fat clients:o Performs the bulk of the processing in client/server applicationso Can handle higher bandwidths, operating systems and software that do not run on

thin clients can run on fat/thick clients as it has its own resources. Some examples of clients include; web browsers and e-mail clients Some examples of servers include; print servers, mail servers and web servers

o Print servers control access to printers on the network and queue data waiting to be printed

o Mail servers route emailo Web servers store and cache web pages

Advantages:o Centralised resources; given that the server is the centre of the network, it can

manage resources that are common to all userso It is possible to remove or add clients without affecting the operation of the network

and without the need for major modification Disadvantages:

o Client-server networks can become congested and overload the server with requestso Increased costs due to the technical complexity of the server

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The client sends a request to the server using its IP address and the port. The server receives the request and responds using the client IP address and port.

Examples of Communication SystemsTeleconferencing systems:

Teleconferencing (video conferencing) is an alternative to face to face meetings, using electronic hardware and software such as camera and internet connections to transfer video and audio data. Commonly used for education and conferencing.

How data is transmitted and received: o The video and audio data is captured, digitised (by assigning a number -binary code-

to each pixel on the image to represent its colour), transmitted over the internet, and then decoded when received.

Advantages: o Facilitates flexible meeting schedulingo Achieves worldwide connectivity; thus avoids expensive travel costs

Disadvantages: o Can be expensive and requires fast processors and high transmission speedso Reduces personal contact; lack of social skills develop

Messaging systems:Email:

Users are able to send text messages and attached files to individuals or groups of people via the internet (e.g. used in schools to send notices and make appointments)

How data is transmitted and received: o Use computers to send and receive text messages and attached documents via the

internet Advantages:

o Very fast transmission of mail compared to conventional postal mailo Capable of transmitting and receiving text, graphics, sound and video as attachmentso Free of charge to send an email; only monthly ISP fee

Disadvantages: o Viruses, which can be attached to email messageso Only available to those who have a computer, internet connection and email address

Voice mail: Voice mail allows transmission of vocal messages between users via telephone systems. How data is transmitted and received:

o Audio messages are recorded and then transmitted by telephone system for storage (when someone is unavailable)

Advantages: o The receiver does not have to be present, and messages are stored and can then be

later retrieved by the recipiento No extra hardware needed besides a telephone

Disadvantages: o Voicemail can be viewed as impersonal by callerso Only users with a voice mail account can access its functionality

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Voice over internet protocol (VOIP): Purpose: To allow voice calls to be made over a broadband internet connection Participants: Residential home users, small businesses Data/information: Sound waves converted to digital audio signals Information technology: Broadband internet connection, computer, VOIP software (for

computer-to-computer connections), microphone, speakers, sound card, modem How data is transmitted and received:

o Sound waves are recorded by microphone o The computer compresses it into data packets for transmission over the IP networko The sending computer places an address on each packet telling the network devices

where to send themo Inside of each packet is a payload; a voice recording digitally convertedo The sending computer sends the packet(s) to a router which directs it to the receivero The receiving computer decodes the transmission to output sound waves

Advantages: o Except for your normal monthly ISP fee, there is usually no charge for computer-to-

computer calls, no matter the distanceo VOIP consumes less transmission time

Disadvantages: o Phone conversations can become distorted, garbled or lost because of transmission

errors (e.g. packet loss)o No power means a call cannot be madeo Susceptible to worms, viruses and hacking

Other systems dependent on communication technology:EFTPOS (Electronic Funds Transfer at Point Of Sale):

EFTPOS is a financial network for processing credit cards, debit cards and ATM transactions at ‘point of sale’.

How data is transmitted and received: o Employee swipes card in a magnetic strip readero Customer enters password/PINo Card details collected and funds transferred from customer to retailer’s account

Advantages: o Easier than manually transferring funds from bank brancho Efficient, secure form of payment

Disadvantages: o Cards are not practical for buying small itemso Both buyer and the seller have to pay charges for use of the cardso Many people don’t have bank accounts or prefer to use cash

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E-commerce: E-Commerce (electronic commerce) consists of the buying and selling of products or services

over electronic systems such as the internet and other computer networks. Can be used with computers, mobile phones, ATMs, telephone, etc.

Advantages: o Customers are more easily able to compare products and serviceso Less labour and paper involved in electronic transactionso Reduced waiting time as products and services are more quickly obtained by

customers Disadvantages:

o Potential customers may not like having to reveal their financial and personal information online

o Fraud, hacking, identity theft, etc.

Electronic banking: Serves as a substitute for cheques and other paper transactions for bank customers who

have a personal computer, an internet connection and an electronic banking account. Fund transfers or enquires are made through the use of devices such as cards or codes to gain access to the account.

Advantages: o Allows people greater convenience in the process of banking as electronic banking is

available 24/7o Saves people from going into the bank to withdraw or deposit money – travel time

and costso It is simple and free

Disadvantages: o People who are not computer literate and people who do not have access to a

personal computer are denied this functiono Customers may be sucked into phishing scams where they disclose their private

details to scammers believing them to be the actual banko Unauthorised individuals can intercept banking transactions; gaining access to

people’s private banking details which they can use for criminal activities such as fraud

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Transmitting and Receiving in Communication SystemsTransmission media:Wired transmission:

Twisted pair: o Twisted pairs are insulated copper wires. They can transfer text, sound, video and

graphics as electric currents. The twists in the cable reduce interference/noise during transmission.

o A twisted pair is installed to an ethernet cable (RJ-45) for use to connect computers in a local area network (LAN)

o Least expensive, reliable data communication Coaxial cable:

o Coaxial cables are thick cores of copper surrounded by insulating material. The insulation is enclosed by a woven mesh. This is surrounded by a plastic layer for protection.

o Mostly used for Internet connections and Foxtel (cable television)o It is very fast and is capable of a high bandwidth and long transmission distances

Optic fibre: o Fibre optic cables are very thin glass strands well protected by insulationo Transmit using light and have greater bandwidth and a higher speed than other

cables. o Fibre optic cable is less susceptible to interference and they do not corrode like the

metal cables. o Most expensive of the three wired transmission mediumso Often used for long distance connections (e.g. Sydney to Melbourne)

Wireless transmission: Microwave:

o Microwaves are electromagnetic waves that can be used for data transmission Satellite:

o Geostationary object (in space) functioning as a repeater o Used for internet connections mainly in remote areas where other internet

connections may be unavailableo Advantages: carry very high bandwidth over very large distances

Radio waves: o Radio waves have the longest wavelengths in the electromagnetic spectrum. o Radio waves do more than just bring music to your radio; they also carry signals for

your television and mobile phones Infrared:

o Wireless signals, mainly used in devices such as remote controls where it is transmission over very short distances

o Advantages: add devices without cables

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Transmission speed: Transmission speed is the time it takes data to travel from the source to the destination. The

hardware being used and the transmission medium will greatly affect this speed. It can be best described in terms of bandwidth, baudrate and bits per second (bps).

Bandwidth: The ability of the transmission medium to handle a particular amount of data in a given time; the higher the bandwidth the more data that can be sent

Baudrate: A measure of the speed of transmission in a communication medium; measures how many times the medium can change its state

Bits per second (bps): A measure of the speed of transmission in communication medium; measures how many bits of data are transmitted (or received) in one second

Application level protocols: HTTP: Hyper Text Transfer Protocol – allow the displaying of files containing hypertext links

across a network SMTP: Simple Mail Transfer Protocol – sending of e-mail messages SSL: Secure Sockets Layer – used for encryption of data for secure data transmission

Communication control and addressing level protocols: TCP/IP: Transmission Control Protocol/Internet Protocol – rules that split data into packets

for transfer across the internet TCP: Responsible for breaking data down into IP packets before they are sent, and for

assembling the packets when they arrive IP: Responsible for ‘routing’ each packet to the correct destination

Transmission level protocols: Ethernet: The Ethernet protocol allows for bus, star, or tree topologies, depending on the

type of cables used and other factors Token ring: A token ring network is a local area network (LAN) in which all computers are

connected in a ring or star topology and a bit (or token) passing scheme is used in order to prevent the collision of data between two computers that want to send messages at the same time.

Strategies for error detection and error correction: Parity:

Parity is the method used to check data in asynchronous transmission, where one character is checked at a time. The eighth bit of the byte is the parity bit, which is used to check the accuracy of transmission. The parity checking can be either odd or even.

Checksum:If the 1 digits of a binary code are added they give a total which is called a checksum. The receiving computer calculates the checksum and compares it to the transmitted checksum, and if they do not match, an error is detected.

Cyclic redundancy check (CRC):The transmitted data is treated as one large binary sum (similar to checksum). The sum is then divided by a constant and the remainder is sent to the receiver. The receiver then works out the sum of the transmitted data, divides it by the same constant and compares the remainder with the transmitted data. CRC has the highest probability of detecting errors.

Network topologies:Page | 7

Asynchronous – uses start and stop bitsSynchronous – no start/stop bit

Star networks:

Advantages: o Fast; if the central computer is fasto Non-centralised failure will not cause the entire network to failo Multiple nodes can be easily connectedo Files can be simultaneously accessed by multiple nodes

Disadvantages: o The network operation depends on the functioning of the central node; hence, the

failure of the central node leads to the failure of the entire network

Bus networks:

Advantages: o It is easy to handle and implement; only one main lineo Cheaper; no extra hardware is required (such as a central server)o Easy error detection since there is only one main line and few connections

Disadvantages: o Slow; can perform well only for a limited number of nodeso If the main line (bus) is broken, transmission will fail

Ring networks:

Advantages: o Cheaper, a central server is not required for the management of this topologyo Easily set up/implemented – using cables

Disadvantages: o If one node of the ring breaks down or a part of the network is disconnected, the

network will not work

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One central node (computer or other network device) and distant nodes are connected along communications lines that radiate as spokes from the central node.

Several devices are connected to a single communications channel.

The topology is that of a continuous circle, with nodes around the circumference.

Hybrid networks:

Advantages: o Able to be used where different types of networks are required

Disadvantages: o Expensive, errors may be hard to detect within the network

Wireless networks:

Advantages: o Cables aren’t needed to connect the nodes together; portable applications are

available, e.g. laptops, wireless printers, etc.o Easy to add stations as there are no cables required

Disadvantages: o Disconnections are more common than with cable connectionso Quality of transmission is not as high as other methodso Devices which are not Wi-Fi enabled cannot be connected to the networko Wireless signal can be intercepted and accessed by hackers

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Hybrid networks use a combination of any two or more of the basic topologies.

The data packets are converted into radio frequencies which travel through the air to the receiving node.

Hubs: A multiport device used to connect computers in a local area network Passes network traffic to all devices connected, therefore slowing down the network Cheaper Half duplex; therefore inefficient under high network traffic

Switches: A multi-port device that allows small sections of LANs to connect and switch traffic directly

from the source to the destination Transmits to the destination port only Faster data transmission as it reduces collisions

Routers: Directs data traffic, is protocol dependent Selects the best path on the network to route data (efficient) by reading the packet address

and understanding the network topology Fast data transmission as it reduces collisions Connects different network

Bridges and gateways: Bridges are used to connect two LANs together in a simple network topology which use the

same protocol to communicate. Gateways provide the ability for one protocol to talk to a different one (protocol

conversion). They are more complex than bridges and will translate data in one protocol to another protocol for transmission.

Network interface cards (NIC): Provides a physical link to a computer network; this connection allows computers to

communicate with servers, as well as other computers on the network.

Mobile phones: Transmit and receive voice calls via radio waves

Cables: Connects communication systems together, allowing for data transmitting and receiving

Wireless access points: A wireless access point (WAP) is a device that allows wireless communication devices to

connect to a wireless network. Common hardware devices that connect to a WAP include laptop computers.

Bluetooth devices: Bluetooth is a wireless network protocol for exchanging data over short distances (using

short length radio waves) from fixed and mobile devices, creating personal area networks (PANs). Common hardware devices that connect to Bluetooth include mobile phones to send and receive data.

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Network operating software: Operating systems are required to run the workstation plus any peripheral devices

connected to it and to allow data transfer. Usually there is a main computer called a server on a network and it stores the main

operating system for the network, but each workstation also needs workstation software to run it. The network operating system software enables all the network hardware and all other network software and makes it all work together as one organised system.

Each workstation has a local operating system that works in collaboration with the network operating system to allow processes such as file sharing, data sharing, peripheral sharing and remote processing where needed.

Internet, intranets and extranets: The Internet consists of a worldwide network of computer networks that use the TCP/IP

network protocols to facilitate data transmission and exchange. An Intranet is a private computer network that uses the protocols of the Internet. An

intranet is not accessible by computers on the outside of the private network. An Extranet is a private network that uses Internet protocols. It can be viewed as part of a

company's intranet that is extended to users outside the company, usually via the Internet.

Other Information Processes in Communication SystemsCollecting:

A phone is a collection device for the use of voice mail An EFTPOS terminal is a collection device for electronic banking

Digital data: Digital Data is data that is stored and transmitted in two possible states; each digit can be

either on or off, represented using electrical impulses that are of high or low voltage Much of our technology relies on digital data Computers use the binary system to store and transmit data, i.e. the digits 1 and 0

Analog data: Analog data is represented in a continuous form in which there are many different

possibilities Analog data can be represented as a wave It is more difficult to handle this type of data as transmitting it accurately involves sending it

in its exact form, and because there are so many more variables it is more easily corrupted

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Processing:Encoding and decoding analog and digital signals:

Communication systems use both analog and digital data, for this reason it is often necessary to encode and decode signals

o Analog data to analog signal - Telephone conversations are the best example here. The system encodes speech and transmits it from sender to receiver.

o Digital data to analog signal - A digital device will often have to display data in an analog form for humans to understand. This will require encoding the 0’s and 1’s.

o Digital data to digital signal - This form of transmission has both sender and receiver speak the same language. One computer on a network is able to communicate directly with another computer.

o Analog data to digital signal - The analog data is encoded to a series of 0’s and 1’s by dividing the data into two groups across an illogical line.

Formation of data packets: A packet is the unit of data that is routed between an origin and a destination on a network The structure of a packet depends on the type of packet it is and on the protocol. Normally,

a packet has a header and a payload For example, an IP packet includes;

o The source IP addresso The destination IP addresso The sequence number of the packetso The type of service, etc.o The payload is the data it carries

Routing: Routing is the process of selecting paths in a network along which to send network traffic Routing is performed for many kinds of networks

Encryption and decryption: Encryption is the process of transforming information (referred to as plaintext) using an

algorithm (called cipher) to make it unreadable to anyone except those possessing special knowledge, who obtain the ‘key’.

Decryption is the reverse process where the receiver requires the ‘key’ to decrypt the data.

Error checking: Parity bit check Check sum Cyclic redundancy check (CRC)

Displaying: A phone is also a display device for the use of voice mail An EFTPOS terminal is also a display device for electronic banking

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Managing Communication SystemsNetwork administration tasks:

Adding/removing users Assigning users to printers Giving users file access rights Installation of software and sharing with users Client installation and protocol assignment Network-based applications Logon and logoff procedures

o Where user enters username and password to validate access. A user session is opened and the user can access resources they have rights to.

o Log-off disconnects that user form network – important for security as open network can be used by unauthorised users

Issues Related to Communication SystemsTeleconferencing systems:

Changing the nature of work as individuals around the world can work on a project and share information

May lose interpersonal skills as communication via microphones and speakers

Messaging systems: Cyber bullying Misinterpretation (may not understand abbreviation, cannot see facial expressions) Privacy

o Employers have rights to read employee emails sent from worko Social networking companies may sell user information without user’s knowledge

Child grooming for sexual assault (using fake Facebook accounts) Diminishing of interpersonal skills

E-commerce: Hacking Loss of jobs as machine replace humans Globalisation: access to unreliable sellers – loss of money

Electronic banking: Jobs and bank branches close as ATM machines replace bank tellers Extra costs for businesses who need to train staff in IT E-crime more common (phishing scams, key logging)

EFTPOS: Similar to e-commerce

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Changing nature of work (working from home):Advantages:

Flexibility over when to work when productivity is high and when it suits private life (taking care of children)

Save costs on travel Allows disabled and rural workers to find jobs Reduced office needs for employers

Disadvantages: Need self motivated staff who can cope with isolation

Virtual communities: Network of individuals who pursue similar interests; e.g. forums created in Facebook and

online dating sites Advantages:

o People from around the world can communicate Disadvantages:

o Young people can become addictedo Loss of social skills

The Internet:The need for ethical behaviour when using the internet

Do not attack others through insulting messages – cyber bullying Do not copy and paste information without proper referencing – plagiarism Do not impersonate others to extract personal data – follow netiquette These behaviours make the internet safe and enjoyable for everyone.

Issues that have arisen from internet use Availability of material normally restricted

o Internet saturated with pornography and children with internet access can easily view sites if no filter (leading to sexualisation of children)

o Internet used to spread child pornography in file sharing sites (abuse of children)o Australian Government implementing a mandatory filter: will this restrict material

that is legally availableDomination of content and control of access to internet

Previously, large media organisations decided what news people would receive. But individuals have greater control and power through blogs – where they can report news.

Access to internet controlled by a few large companies. There is less competition, leading to higher internet prices, which limits access to the poor.

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Current and emerging trends in communications:Blogs:

Online personal journal which other users can read; entries are dated & has a journal design Only updated by blog owner Gives individual the power of the media as they can share opinion – but the information may

not be accurate

Wikis: An internet resource allowing individuals to seek answers to questions Can be updated by any internet user with a wiki account Powerful educational resource – but the information may not be accurate

RSS feeds: A format for delivering regularly changing web content Many news-related sites, weblogs and other online publishers syndicate/organise their

content as an RSS feed to whoever wants it

Podcasts: Cheap to create and can be downloaded for listening anywhere, anytime. Uploading an MP3 file to a webpage

Online radio, TV and video on demand: Stream live broadcasts

3G technologies for mobile communications: Higher speed internet and better multimedia access Expensive and requires compatible devices

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