DEFINITION OF TELECOMMUNICATION
Telecommunications, or telecom, refers to the process of exchanging information such as voice, data and video transmissions via electronic technologies like telephones (wired and wireless), microwave communications, fiber optics, satellites, radio and television broadcasting, and the internet.
Six potential media are employed to implement telecommunication links and systems
- Twisted pair.
- Coaxial cable.
- Fiber Optics cable.
- Terrestrial Microwave.
- Satellite Transmission.
- Radio Transmission.
Three of the above transmission media are classified as guided media – in which the signal moves along an enclosed path. Guided media require wiring. They include:
1. Twisted pair
2. Coaxial cable
3. Fiber optic cable
Three of the above transmission media are classified as wireless media – the signal is broadcast (radiated in many directions) over the air or space and received through an antenna. They include:
1. Terrestrial Microwave
2. Satellite Transmission
3. Radio Transmission
Characteristics of Communications Media:
Twisted Pair a communications medium consisting of a pair of wires.
Coaxial Cable a communications medium that consists of a relatively thick central conductor shielded by several layers of insulation and the second conductor just under the cable’s shell
Fiber Optics high-capacity communications medium that consists of many strands of pure glass with a data carrying core in the middle, surrounded by a reflective coating and a protective sheath.
Terrestrial Microwave long-distance telecommunications by means of microwave signals travelling on the surface of the earth.
Satellite Transmission form of microwave transmission in which the signal is transmitted by an earth station to a satellite which rebroadcasts the signal to the receiving station.
Radio Transmission wireless communications technology that transmits voice or data over the air using a lower frequency band than microwaves.
Note: Transmission speeds keep on rising, particularly in the fiber optics area. We are now moving toward a global infrastructure of gigabit-speed fiber optic links relying on digital transmission. In this multimedia environment, data, text, voice, images, and video will travel at speeds of billions of bits per second.
Analog and Digital Communications [Figure 7.8][Slide 7-7]
Most of the lines in the telephone systems of the world at present are analog. Signals are transmitted as continuous waves. This is a satisfactory way to transmit voice, but digital data sent by computers (sequences of pulses representing 0s and 1s) must be converted into an analog signal for transmission over an analog line. The analog data must then be converted back into digital before entering the memory of the receiving computer. The conversion of data from digital form into analog for transmission and then back into digital at the receiving end is done by a pair of interface devices called modems (modulator-demodulator).
Modem-based telecommunications have created a significant bottleneck in an environment where computer and peripheral speeds have increased dramatically. The solution is end-to-end digital communications, in which signals are sent as streams of on/off pulses. Digital lines are capable of much faster communication and digital circuitry is now cheaper than analog. All the new equipment now installed in telephone networks is indeed digital.
Trend: There is a shift toward digital telecommunications is taking place throughout the world. A digital system for telecommunications, called TI carrier, is in wide use in parts of the telephone network.
Future: Integrated Services Digital Network (ISDN) – a completely digital telecommunications network standardized by an international committee. Although ISDN services are available in some areas, including most of the US, worldwide ISDN is not expected to become operational until after the year 2000.
How to Reduce the Costs of Telecommunications Multiplexing and Signal Compression
With the geographical distribution of information systems, increased volumes of transmission, and the move to multimedia, the costs of telecommunications are a significant business concern. Two principal methods of reducing these costs are:
1. Multiplexing – the sharing of a high-capacity link by a number of transmissions
2. Signal Compression – using the link more efficiently by removing redundancies from the signal.
Characteristics of multiplexing:
1. There are economies of scale in telecommunications systems: the higher the system capacity, the lower the unit cost of transmissions.
2. Many individual transmissions can share a physical channel through a variety of techniques collectively called multiplexing.
3. Multiplexing combines several lower-capacity transmissions into a single transmission, which is split at the receiving end.
Characteristics of signal compression:
1. Signal compression is the reduction of the need for channel capacity by removing redundancies from the signal.
2. To reduce the transmission needs, we can remove the redundancies at the sender site, transmit the compressed signal, and then restore the signal at the receiving end.
3. Compression has an impressive effect on multimedia transmission needs.
7.3 Computer Networks and telecommunication
Computer networks differ in scope from relatively slow wide area networks, employed to transmit messages across vast geographic distances, to very fast local area networks that may connect computers located in the same building. System designers may select one of several arrangements for interconnecting network nodes, depending on an organization’s requirement. There are several ways to establish a connection between the sender and the receiver of a message.
Computers, switches, and terminals interconnected by network links are collectively called nodes. The purpose of network control is to provide a connection between nodes that need to communicate. The arrangement of nodes and links in a network is called a topology. A variety of arrangements are possible, each with its own advantages and drawbacks. Network topology has to fit the structure of the organizational unit that will use the network, and this topology should also be adapted to the unit’s communication traffic patterns and to the way the databases will be stored in order to facilitate access to them.
The following topologies are the most widely used:
1. Hierarchical Network
2. Star Network
3. Ring Network
4. Bus Network
Hierarchical Network: [Figure 7.4]
a. A corporate host computer (often a mainframe), divisional minicomputers or powerful workstations, and workgroup support via micros.
b. This topology matches the organizational structure of many firms and is still frequently used in WANs.
c. The user workstations may be, in turn, interconnected using one of the LAN topologies.
d. Failure of the host does not disable divisional processing, which is a fail-safe feature.
e. Cost-effectiveness of micros and the growing importance of groupwork leads some downsizing firms to move away from hierarchical networks to client/server computing.
Star Network: [Figure 7.9a]
a. In a star network, a hub computer or switch (such as a PBX) interconnects a number of workstations.
b. The computer at the hub acts as the network server, providing access to the shared database and software. All communications between the workstations must go through this central mode.
c. The star network is rather easy to manage and expand, since in both cases it is largely the single central node that is affected in an expansion of a processing capacity.
d. The central node is a locus of vulnerability: it may be overloaded or it may fail, disabling the entire network.
Ring Network: [Figure 7.9b]
a. Each node in a ring network is connected to two of its neighbours.
b. The nodes are usually close to one another; this topology is frequently used in LANs.
c. When one node sends a message to another, the message passes through each intermediate node, which restores the signal, as signals deteriorate in transmission.
d. If a node fails, the ring is out of service, unless the ring contains two channels transmitting in opposite directions.
Bus Network: [Figure 7.9c]
a. The nodes on a bus network are connected to a common link such as coaxial cable. This arrangement is used in LANs.
b. A failing device does not affect the rest of the network; failure of the bus itself, of course, brings the network down.
Switching in Networks
Many users can be connected at the same time to a network of communication channels. Switching devices establish connections between nodes that need to communicate over a network. Principal techniques for switching include:
1. Circuit Switching
2. Packet Switching
3. Fast Packet Switching
1. The circuit switching technique is employed in a telephone network.
2. Communication links are connected to switching centers, which connect to one node to another on demand.
3. The circuit is established for the entire duration of the communication
4. Circuit switching is suitable for file transfers and similar longer transmissions
Packet Switching: [Figure 7.10]
1. Packet switching is of particular importance for data communication owing to its speed and its superior utilization of communication links when handling Abursty,@ intermittent, traffic. Indeed, data transmission involves short bursts of activity by a computer or a terminal when the data are sent, followed by long periods when there is no transmission.
2. Packet switching offers flexibility in connecting to a network. It is used by most of the public data networks provided by value-added carriers.
3. In packet switching, messages are divided at the source into fixed-length chunks, called packets, that also include bits identifying the receiver. Typically, a packet contains 128 bytes of data.
4. Each packet, can be transmitted independently, with routing determined at each node the packet passes through (as opposed to circuit switching, where the route is predetermined).
Fast Packet Switching:
Traditional packet switching checks each packet for errors at every node the packet passes through. Modern telecommunications equipment is far more noise-free than that for which packet switching was originally designed. To take advantage of this, two fast packet-switching technologies are being introduced:
Frame Relay: Fast packet switching that checks a packet for errors only at the entry and exit nodes of the telecommunications network, thus reducing transmission delay.
Cell Relay: (asynchronous transfer mode, or ATM) transfers very short fixed-length packets, called cells, over fast LANs or WANs.
7.4 Communications Protocols in Computer Networks
Communication rules, called protocols, enable dissimilar hardware and software to communicate over a single network.
Network Protocols [Figure 7.11][Slide 7-8]
Computer networks exist to provide connectivity among a variety of computers and access devices. To ensure orderly communication over a network, all the nodes in the network must follow a set of rules called protocols. These rules are complex. They extend from the electric connection to the network and the format of the message, all the way to the interaction between application programs that run on different nodes.
Explain to students that with the globalization of telecommunications, the International Standards Organization (ISO) has developed the OSI model in order to organizing protocols. The open system approach opens the field to a broad array of competing vendors, a situation that benefits users to ensure that they are not locked into a closed, proprietary protocol structure of a specific manufacturer.
1. Gives both users and vendors flexibility in conforming to a standard.
2. Users can select a protocol for any layer of the model, as long as the protocol performs the necessary services and provides the same interface to the adjacent layers.
3. If a layer has to be changed, only the hardware or software implementing that layer need be modified.
4. A protocol layer in one node interacts with the corresponding layer in another one.
Why is Telecommunications So Important?
#1. It Satisfies Our Basic Needs
Information technology and the ability to connect and communicate is a fundamental part of how our society operates. In today’s digital ecosystem, telecommunication has become the foundation for businesses, governments, communities, and families to seamlessly connect and share information.
Thanks to telecom advancements, things like searching the internet, placing phone calls, emailing, and text messaging has become integrated into our personal and professional lives on a near-ubiquitous level.
#2. It’s Vital for Security
From a security perspective, telecommunication is one of the most crucial infrastructures for protection. From natural disaster initiatives to military needs, there’s a wide spectrum of institutions that depend on telecom to provide safety.
The government invests heavily in communications systems as a means for enabling security agencies to counter threats and safeguard its people from harm. Overseas sources pose potential risks of security breaches and therefore aren’t a reliable source.
#3. It Empowers Participation
Communities in remote regions were once unable to access vital resources. Now, because of telecommunications, these locations can procure goods and services via ships or aircraft and systematize development initiatives. This type of accessibility allows for the growth and development of our entire society.
#4. It’s an Economic Booster
The telecom sector is responsible for an estimated global spend of $520 billion annually. The frontrunner, unsurprisingly, is the U.S., boasting one of the largest telecom markets in the world.
That’s a good thing for our country, as the economy benefits from the growth and development of the telecoms sector. So, why is the telecommunications industry so prevalent in the U.S.?
Firstly, it encompasses the following subsectors:
- Cable distribution
- Telephony, including Voice over Internet Protocol (Voip)
- Satellite telecommunications
#5. Encourages Education
Thanks to technological advances, people have access to learning opportunities outside of traditional schooling. Today, you simply need a computer, smartphone, and the internet to conduct a search, read a tutorial, or watch a how-to video on virtually any subject matter.
Some of the largest institutions are now leveraging telecommunications to deliver long-distance or remote education. This is extremely cost-effective for students, allowing them to conserve money that would otherwise be spent on housing and travel.
What’s more, online courses provide students with the flexibility and freedom to accommodate both their work obligations and studies. Social media has also become an important vehicle for classmates and teachers to connect and share information.
#6. It Transformed the Business World
Companies are now relying on telecommunications to foster operational efficiency and stimulate steady growth. Want to fully comprehend the full scope of benefits telecom provides businesses?
- Telecommunications provides a technological foundation for societal communications. …
- Telecommunications enables participation and development. …
- Telecommunications provides vital infrastructure for national security.
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