<–2/”>a >Basic element of Communication-systems/”>Communication systems, data transmission mode, transmission media, Network topologies, network types, communication protocols, network security mechanism.
- Elements of a Communication System
Elements of a communication system
The above figure depicts the elements of a communication system. There are three essential parts of any communication system, the transmitter, transmission channel, and receiver. Each parts plays a particular role in signal transmission, as follows:
The transmitter processes the input signal to produce a suitable transmitted signal suited to the characteristics of the transmission channel.
Signal processing for transmissions almost always involves modulation and may also include coding.
The transmission channel is the electrical medium that bridges the distance from source to destination. It may be a pair of wires, a coaxial cable, or a radio wave or laser beam. Every channel introduces some amount of transmission loss or attenuation. So, the signal power progressively decreases with increasing distance.
The receiver operates on the output signal from the channel in preparation for delivery to the transducer at the destination. Receiver operations include amplification to compensate for transmission loss. These also include demodulation and decoding to reverse the signal procession performed at the transmitter. Filtering is another important function at the receiver.
The figure represents one-way or simplex (SX) transmission. Two way communication of course requires a transmitter and receiver at each end. A full-duplex (FDX) system has a channel that allows simultaneous transmission in both directions. A half-duplex (HDX) system allows transmission in either direction but not at the same time.
- Transmission Modes in Computer Networks
Transmission mode means transferring of data between two devices. It is also called communication mode. These modes direct the direction of flow of information. There are three types of transmission mode. They are :
Simplex Mode
Half duplex Mode
Full duplex Mode
SIMPLEX Mode
In this type of transmission mode data can be sent only through one direction i.e. communication is unidirectional. We cannot send a message back to the sender. Unidirectional communication is done in Simplex Systems.
Examples of simplex Mode is loudspeaker, television broadcasting, television and remote, keyboard and monitor etc.
HALF DUPLEX Mode
In half duplex system we can send data in both directions but it is done one at a time that is when the sender is sending the data then at that time we can’t send the sender our message. The data is sent in one direction.
Example of half duplex is a walkie- talkie in which message is sent one at a time and messages are sent in both the directions.
FULL DUPLEX Mode
In full duplex system we can send data in both directions as it is bidirectional. Data can be sent in both directions simultaneously. We can send as well as we receive the data.
Example of Full Duplex is a Telephone Network in which there is communication between two persons by a telephone line, through which both can talk and listen at the same time.
In full duplex system there can be two lines one for sending the data and the other for receiving data.
- TRANSMISSION MEDIA
Factors to be considered while choosing Transmission Medium
Transmission Rate
Cost and Ease of Installation
Resistance to Environmental Conditions
Distances
Coaxial Cable
Coaxial is called by this name because it contains two Conductors that are parallel to each other. Copper is used in this as centre conductor which can be a solid wire or a standard one. It is surrounded by PVC installation, a sheath which is encased in an outer conductor of Metal foil, barid or both.
Outer metallic wrapping is used as a shield against noise and as the second conductor which completes the circuit. The outer conductor is also encased in an insulating sheath. The outermost part is the plastic cover which protects the whole cable
Fiber Optic Cable
These are similar to coaxial cable. It uses electric signals to transmit data. At the centre is the glass core through which Light propagates.
In multimode fibres, the core is 50microns, and In single mode fibres, the thickness is 8 to 10 microns.
The core in fiber optic cable is surrounded by glass cladding with lower index of refraction as compared to core to keep all the light in core. This is covered with a thin plastic jacket to protect the cladding. The fibers are grouped together in bundles protected by an outer shield.
Fiber optic cable has bandwidth more than 2 gbps (Gigabytes per Second)
Unguided or wireless media sends the data through air (or water), which is available to anyone who has a device capable of receiving them. Types of unguided/ unbounded media are discussed below :
Radio Transmission
MicroWave Transmission
Radio Transmission
Its frequency is between 10 kHz to 1GHz. It is simple to install and has high attenuation. These waves are used for multicast communications.
Types of Propogation
Radio Transmission utilizes different types of propogation :
- Troposphere : The lowest portion of earth’s Atmosphere extending outward approximately 30 miles from the earth’s surface. Clouds, jet planes, wind is found here.
- Ionosphere : The layer of the atmosphere above troposphere, but below space. Contains electrically charged particles.
Microwave Transmission
It travels at high frequency than the radio waves. It requires the sender to be inside of the receiver. It operates in a system with a low gigahertz range. It is mostly used for unicast communication.
There are 2 types of Microwave Transmission :
- Terrestrial Microwave
- Satellite Microwave
Terrestrial Microwave
For increasing the distance served by terrestrial microwave, repeaters can be installed with each antenna .The signal received by an antenna can be converted into transmittable form and relayed to next antenna as shown in below figure. It is an example of telephone systems all over the world
Satellite Microwave
This is a microwave relay station which is placed in outer space. The satellites are launched either by rockets or space shuttles carry them.
These are positioned 36000KM above the equator with an orbit speed that exactly matches the rotation speed of the earth. As the satellite is positioned in a geo-synchronous orbit, it is stationery relative to earth and always stays over the same point on the ground. This is usually done to allow ground stations to aim antenna at a fixed point in the sky.
NETWORK TOPOLOGIES
Network Topology refers to the layout of a network and how different nodes in a network are connected to each other and how they communicate. Topologies are either physical (the physical layout of devices on a network) or logical (the way that the signals act on the network media, or the way that the data passes through the network from one device to the next).
Mesh Topology
In a mesh network, devices are connected with many redundant interconnections between network nodes. In a true mesh topology every node has a connection to every other node in the network. There are two types of mesh topologies:
Full mesh topology: occurs when every node has a circuit connecting it to every other node in a network. Full mesh is very expensive to implement but yields the greatest amount of redundancy, so in the event that one of those nodes fails, network traffic can be directed to any of the other nodes. Full mesh is usually reserved for backbone networks.
Partial mesh topology: is less expensive to implement and yields less redundancy than full mesh topology. With partial mesh, some nodes are organized in a full mesh scheme but others are only connected to one or two in the network. Partial mesh topology is commonly found in peripheral networks connected to a full meshed backbone.
2. Star Topology
In a star network devices are connected to a central computer, called a hub. Nodes communicate across the network by passing data through the hub.
Main Advantage: In a star network, one malfunctioning node doesn’t affect the rest of the network.
Main Disadvantage: If the central computer fails, the entire network becomes unusable.
3. Bus Topology
In networking a bus is the central cable — the main wire — that connects all devices on a local-area network (LAN). It is also called the backbone. This is often used to describe the main network connections composing the Internet. Bus networks are relatively inexpensive and easy to install for small networks. Ethernet systems use a bus topology.
Main Advantage: It’s easy to connect a computer or device and typically it requires less cable than a star topology.
Main Disadvantage: The entire network shuts down if there is a break in the main wire and it can be difficult to identify the problem if the network shuts down.
4. Ring Topology
Ring Topology: A local-area network (LAN) whose topology is a ring. That is, all of the nodes are connected in a closed loop. Messages travel around the ring, with each node reading those messages addressed to it.
Main Advantage: One main advantage to a ring network is that it can span larger distances than other types of networks, such as bus networks, because each node regenerates messages as they pass through it.
- Tree Topology
This is a “hybrid” topology that combines characteristics of linear bus and star topologies. In a tree network, groups of star-configured networks are connected to a linear bus backbone cable.
Main Advantage: A Tree topology is a good choice for large computer networks as the tree topology “divides” the whole network into parts that are more easily manageable.
Main Disadvantage: The entire network depends on a central hub and a failure of the central hub can cripple the whole network.
· NETWORK TYPES
Local Area Network (LAN)
It is also called LAN and designed for small physical areas such as an office, group of buildings or a factory. LANs are used widely as it is easy to design and to troubleshoot. Personal computers and workstations are connected to each other through LANs. We can use different types of topologies through LAN, these are Star, Ring, Bus, Tree etc.
LAN can be a simple network like connecting two computers, to share files and network among each other while it can also be as complex as interconnecting an entire building.
LAN networks are also widely used to share Resources like printers, shared hard-drive etc.
Applications of LAN
One of the computer in a network can become a server serving all the remaining computers called clients. Software can be stored on the server and it can be used by the remaining clients.
Connecting Locally all the workstations in a building to let them communicate with each other locally without any internet access.
Sharing common resources like printers etc are some common applications of LAN.
Metropolitan Area Network (MAN)
It is basically a bigger version of LAN. It is also called MAN and uses the similar technology as LAN. It is designed to extend over the entire city. It can be means to connecting a number of LANs into a larger network or it can be a single cable. It is mainly hold and operated by single private company or a public company.
Wide Area Network (WAN)
It is also called WAN. WAN can be private or it can be public leased network. It is used for the network that covers large distance such as cover states of a country. It is not easy to design and maintain. Communication medium used by WAN are PSTN or Satellite links. WAN operates on low data rates.
Wireless Network
It is the fastest growing segment of computer. They are becoming very important in our daily life because wind connections are not possible in cars or aeroplane. We can access Internet at any place avoiding wire related troubles.. These can be used also when the telephone systems gets destroyed due to some calamity/disaster. WANs are really important now-a-days.
Inter Network
When we connect two or more networks then they are called internetwork or internet. We can join two or more individual networks to form an internetwork through devices like routers gateways or bridges.
· COMMUNICATION PROTOCOL
Communication protocols are formal descriptions of digital message formats and rules. They are required to exchange messages in or between computing systems and are required in telecommunications.
Communications protocols cover authentication, error detection and correction, and signaling. They can also describe the syntax, semantics, and synchronization of analog and digital communications. Communications protocols are implemented in hardware and software. There are thousands of communications protocols that are used everywhere in analog and digital communications. Computer networks cannot exist without them.
Communications devices have to agree on many physical aspects of the data to be exchanged before successful transmission can take place. Rules defining transmissions are called protocols.
There are many properties of a transmission that a protocol can define. Common ones include: packet size, transmission speed, error correction types, handshaking and synchronization techniques, address mapping, acknowledgement processes, flow control, packet sequence controls, routing, and address formatting
Popular protocols include: File Transfer Protocol (FTP), TCP/IP, User Datagram Protocol (UDP), Hypertext Transfer Protocol (HTTP), Post Office Protocol (POP3), Internet Message Access Protocol (IMAP), Simple Mail Transfer Protocol (SMTP).
Application Layer Protocol – HTTP and IRC
HTTP
The HyperText Transfer Protocol (HTTP) is the most common protocol in use on the internet. The protocol’s job is to transfer HyperText (such as HTML) from a server to computer. HTTP functions as a simple conversation between client and server.
IRC
Internet Relay Chat (IRC) is a system that lets someone to transfer messages in the form of text. It’s essentially a chat protocol. The system uses a client-server model. Clients are chat programs installed on a user’s computer that connect to a central server. The clients communicate the message to the central server which in turn relays that to other clients. The protocol was originally designed for group communication in a discussion forum, called channels. IRC also supports one-to-one communication via private messages. It is also capable of file and data transfer too.
Transport Layer Protocol – TCP/IP
TCP (The Transmission Control Protocol) is one of the most important protocols on the internet. It breaks large messages up into packets.
During the late 1970’s and into the 80’s, the U.S. Department of Defense experienced numerous technical failures when attempting to connect multiple computers (nodes) and multiple networks with the intent of sharing data and information. In 1981, the government was successful following the implementation of the Transmission Control Protocol (TCP) and the Internet Protocol (IP) technologies. in bringing the Internet alive with these combined (TCP/IP) technologies, project engineers and researchers were able to meet the needs of most users by enabling online capabilities to perform file transfers, e-mail, file sharing and remote log on functions.
IP : The Internet Protocol is responsible for moving data, in the form of electronic packets, along the internet network until the packets are received at the intended destination or IP address.
TCP: The Transmission Control Protocol is responsible for ensuring safe delivery of each data packet from the sending node to the receiving node within a network. In addition, because data packets can be misdirected or damaged during transmission, the TCP detects these errors as they occur during the transmission and automatically retransmits each questionable data packet.
As the Internet’s protocol suite, TCP/IP consists of five protocol layers. These protocol layers are related to the seven layers comprising the Open System Interconnection (OSI) network architecture.
Reference Models in Communication Networks
The most important reference models are :
OSI reference model.
TCP/IP reference model.
OSI reference Model
There are many users who use computer network and are located all over the world. To ensure national and worldwide data communication ISO (ISO stands for International Organization of Standardization.) developed this model. This is called a model for open system interconnection (OSI) and is normally called as OSI model.OSI model architecture consists of seven layers. It defines seven layers or levels in a complete communication system.
TCP/IP reference model
TCP/IP is transmission control protocol and internet protocol. Protocols are set of rules which govern every possible communication over the internet. These protocols describe the movement of data between the host computers or internet and offers simple naming and addressing schemes.
· NETWORK SECURITY MECHANISM
The process to implement the security properties is known as security mechanism. The various type of mechanism on the basis of properties is as follows:
Attack Prevention
Attack Avoidance
Attack Detection
Attack Prevention: can be defined as a series of security mechanism implemented to prevent or defend against various types of attack before they can actually reach and affect the target systems. An important mechanism is access control which is defined as the process of limiting the access to the resources of the Information System. Access can be implemented at different levels such as the operating system the network and the application layer.
A firewall is also an important access control system that is implemented at the network layer the concept behind firewall is to separate the trusted network from the entrusted network known as internet. The firewall prevents the attack from the outside world against the machines inside the internal network by preventing connections attempts from the unauthorized entities located outside.
Attack Avoidance: The expansion of connectivity of computers makes the need of protecting the message and message from tampering reading important. This is the technique in which the information is modified in a way that makes is unusable for the attacker. This is performed under the assumption that the attacker may have access to the subject system/information. The sender preprocess the information before it is send through the unsecured system and the same is again post processed on the receiver end systems. This encryption and decryption is perfumed by cryptography mechanism, they are further divided in the following forms:
Secret Key Cryptography
Public Key Cryptography
Hash Functions
Attack Detection: In this mechanism it is assumed that the attacker is able to bypass the installed security measures to access the desired target/information. When such incidents happens attack detection takes the responsibility to report someone that something went wrong somewhere in the system.
Attack detection is not an applicable mechanism instead of that it’s a check/measure which will make sure that if anything happened badly in the system then someone should be notified.
Telecommunications, also known as telecom, is the exchange of information over significant distances by electronic means and refers to all types of voice, data and video transmission. This is a broad term that includes a wide range of information transmitting technologies such as telephones (wired and wireless), microwave communications, fiber optics, satellites, radio and television broadcasting, the internet and telegraphs.
A complete, single telecommunications circuit consists of two stations, each equipped with a transmitter and a receiver. The transmitter and receiver at any station may be combined into a single device called a transceiver. The medium of signal transmission can be via electrical wire or cable (also known as “copper”), optical fiber, electromagnetic fields or light. The free space transmission and reception of data by means of electromagnetic fields is called wireless communications.
Types of telecommunications networks
The simplest form of telecommunications takes place between two stations, but it is common for multiple transmitting and receiving stations to exchange data among themselves. Such an arrangement is called a telecommunications network. The internet is the largest example of a telecommunications network. On a smaller scale, examples include:
- Corporate and academic wide-area networks (WANs)
- Telephone networks
- Cellular networks
- Police and fire communications systems
- Taxi dispatch networks
- Groups of amateur (ham)
- radio operators
- Broadcast networks
Data is transmitted in a telecommunications circuit by means of an electrical signal called the carrier or the carrier wave. In order for a carrier to convey information, some form of modulation is required. The mode of modulation can be broadly categorized as either analog or digital.
In analog modulation, some aspect of the carrier is varied in a continuous fashion. The oldest form of analog modulation is amplitude modulation (AM), which is still used in radio broadcasting at some frequencies. Digital modulation actually predates analog modulation; the earliest form was Morse code. Modern telecommunications use IPs (internet protocols) to carry data across underlying physical transmissions.
Role of telecommunications and socio-Economic Development
Telecommunication has very significant role to play in development of various sectors of the economy. In the 21st century, telecommunication sector has become pivotal to a country’s socio-economic development. It is one of the prime support Services needed to promote Growth and modernization of various sectors of an economy. Enormous growth of Information and communication technology and its role in development of various sectors including services like finance, insurance, trade, hotel and business services as well as Industry, agriculture and governance is commendable. Telecommunication Infrastructure-2/”>INFRASTRUCTURE is somewhat different from other forms of infrastructure because of existence of network externalities, a phenomenon that increases the value of services with the increasing number of users. Thus the impact of telecommunication infrastructure on economic development is more pronounced as compared to other traditional infrastructure.
A modem network contributes to economic growth in four ways20 :
Business attractionJ Business retention
A sophisticated low cost telecommunications infrastructure makes information flow efficiently to and from more remote areas and is a factor when information- intensive corporations relocate. The same argument is extended by Boyle when he contends that the quality of telecommunications and mail services are the factors most often mentioned by the decision makers in case of corporate head quarters location or relocation.
Diversification of Economic Base
Most economists agree that diversity is the key to growth and stability. The less dependent a local economy is on one particular industry, the more likely it is to withstand cyclical downturns. Enhanced telecommunications services supported by a sophisticated network will allow small businesses/entrepreneurs to compete with large corporations that often have installed sophisticated private networks.
Enhancement of Quality Of Life / delivery of vital social services
In many large cities, rush hour grid lock and poorly maintained roadways are all too familiar. In response, some government have implemented commuter and fuel taxes to discourage heavy use of public roads. Others have offered telecommuting as a solution, without a modem telecom network, however, telecommuting is impossible.
Increased competitiveness of existing firms
The manufacturing industry, for example, can more efficiently handle product design, inventory control and customer services using an advanced telecom network and computers. Service sector industry can provide more efficient transactions and electronic data interchange through extensive use of improved and advanced telecommunications.,
A communication system is a system that allows for the transmission of information from one point to another. The basic elements of a communication system are:
- Source: The source is the entity that generates the information to be transmitted.
- Transmitter: The transmitter is the device that converts the information from the source into a form that can be transmitted over the channel.
- Channel: The channel is the medium through which the information is transmitted.
- Receiver: The receiver is the device that converts the information from the channel into a form that can be used by the destination.
- Destination: The destination is the entity that receives the information from the receiver.
Noise is any unwanted signal that interferes with the desired signal. Interference is any unwanted signal that is generated by the channel or the Environment. Distortion is any change in the shape of the desired signal that is caused by the channel or the receiver.
Modulation is the process of changing one or more characteristics of a carrier signal in accordance with the information to be transmitted. Demodulation is the process of recovering the information from a modulated signal.
Coding is the process of representing information in a form that is suitable for transmission over a channel. Decoding is the process of recovering the information from a coded signal.
Multiplexing is the process of combining multiple signals into a single signal for transmission over a shared channel. Demultiplexing is the process of recovering the individual signals from a multiplexed signal.
Amplification is the process of increasing the power of a signal. Filtering is the process of removing unwanted frequencies from a signal. Equalization is the process of compensating for the frequency-dependent attenuation of a channel.
Error correction is the process of detecting and correcting errors that occur in a transmitted signal. Handshaking is the process of establishing and maintaining communication between two devices. Synchronization is the process of ensuring that two devices are in step with each other.
Addressing is the process of identifying the destination of a message. Routing is the process of determining the path that a message will take to reach its destination. Switching is the process of connecting two devices so that they can communicate with each other.
Access control is the process of controlling who has access to a communication system. Security is the process of protecting information from unauthorized access, use, disclosure, disruption, modification, or destruction.
Performance evaluation is the process of measuring the performance of a communication system. Quality of service is the set of characteristics that determine the acceptability of a service to a user.
Reliability is the Probability that a system will perform its required function under stated conditions for a specified period of time. Availability is the probability that a system is available for use when needed. Maintainability is the ease with which a system can be restored to a specified condition after it has failed.
Safety is the freedom from danger or risk. Ergonomics is the study of the interaction between humans and machines. Environmental impact is the effect of a system on the environment. Economic impact is the effect of a system on the economy.
Social impact is the effect of a system on Society. Legal and regulatory impact is the effect of a system on laws and regulations.
Communication systems are used in a wide variety of applications, including telecommunications, data communications, and broadcasting. They are also used in many industrial and military applications.
Telecommunications is the transmission of information over long distances using electrical or electromagnetic signals. Data communications is the transmission of digital data over a communication channel. Broadcasting is the transmission of audio or video signals to a large audience.
Industrial applications of communication systems include process control, machine control, and inventory control. Military applications of communication systems include command and control, intelligence gathering, and battlefield communications.
Communication systems are constantly evolving as new technologies are developed. Some of the latest trends in communication systems include the development of high-speed data networks, the use of wireless technologies, and the convergence of voice, data, and video services.
Here are some frequently asked questions and short answers about communication systems:
What is a communication system?
A communication system is a system that allows for the transmission of information from one point to another.What are the basic elements of a communication system?
The basic elements of a communication system are a transmitter, a channel, and a receiver.What is a transmitter?
A transmitter is a device that converts information into a form that can be transmitted over a channel.What is a channel?
A channel is the medium through which information is transmitted.What is a receiver?
A receiver is a device that converts the information that is transmitted over a channel into a form that can be used by the receiver.What are the different types of communication systems?
There are many different types of communication systems, including analog communication systems, digital communication systems, and wireless communication systems.What are the advantages and disadvantages of analog communication systems?
The advantages of analog communication systems include their simplicity and their ability to handle a wide range of frequencies. The disadvantages of analog communication systems include their susceptibility to noise and interference, and their inability to provide error-free transmission.What are the advantages and disadvantages of digital communication systems?
The advantages of digital communication systems include their immunity to noise and interference, and their ability to provide error-free transmission. The disadvantages of digital communication systems include their complexity and their inability to handle a wide range of frequencies.What are the advantages and disadvantages of wireless communication systems?
The advantages of wireless communication systems include their flexibility and their ability to provide mobility. The disadvantages of wireless communication systems include their susceptibility to noise and interference, and their limited range.What are some of the challenges in designing and developing communication systems?
Some of the challenges in designing and developing communication systems include the need to minimize noise and interference, the need to ensure error-free transmission, and the need to meet the requirements of the specific application.
Question 1
A communication system is a system that allows for the transmission of information from one location to another. The basic elements of a communication system are:
- A transmitter, which converts the information to be transmitted into a form that can be transmitted over the communication channel.
- A communication channel, which is the medium through which the information is transmitted.
- A receiver, which converts the information back into a form that can be used by the destination.
The following are some examples of communication systems:
- A telephone system, which converts Sound waves into electrical signals that are transmitted over a wireline or wireless network to a receiver, which converts the electrical signals back into sound waves.
- A radio system, which converts sound waves into radio waves that are transmitted through the air to a receiver, which converts the radio waves back into sound waves.
- A television system, which converts images and sound into electrical signals that are transmitted over a cable or satellite network to a receiver, which converts the electrical signals back into images and sound.
Question 2
The following are some of the factors that affect the performance of a communication system:
- The type of communication channel used.
- The distance between the transmitter and receiver.
- The presence of noise in the communication channel.
- The bandwidth of the communication channel.
- The modulation scheme used.
Question 3
The following are some of the applications of communication systems:
- Telecommunications
- Broadcasting
- Navigation
- Remote sensing
- Control systems
Question 4
The following are some of the challenges in the design of communication systems:
- The need to transmit information over long distances with high reliability.
- The need to combat noise and interference in the communication channel.
- The need to support a wide range of applications with different requirements.
- The need to meet the ever-increasing demand for bandwidth.
Question 5
The following are some of the recent advances in communication systems:
- The development of high-speed optical fiber networks.
- The development of wireless communication technologies such as Wi-Fi and LTE.
- The development of new modulation schemes that can support higher data rates.
- The development of new error correction codes that can combat noise and interference.
Question 6
The following are some of the future trends in communication systems:
- The continued growth of wireless communication.
- The development of new communication technologies such as 5G and beyond.
- The integration of communication systems with other technologies such as the Internet of Things.
- The development of new applications for communication systems.