Data Communication

Data communication:

Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. For data communications to occur, the communicating devices must be part of communication system made up of a combination of hardware (physical equipment) and software(programs).

The effectiveness of a data communications system depends on four fundamental characteristics:

delivery, accuracy, timeliness, and jitter.

A data communications system has five components:

• Message: The message is the information (data) to be communicated. Popular forms of information include text, numbers, pictures, audio, and video.
• Sender: The sender is the device that sends the data message. It can be a computer, workstation,telephone handset, video camera, and so on.
• Receiver: The receiver is the device that receives the message. It can be a computer, workstation,telephone handset, television, and so on.
• Transmission medium: The transmission medium is the physical path by which a message travels from sender to receiver. Some examples of transmission media include twisted-pair wire, coaxial cable, fiber-optic cable, and radio waves.
• Protocol: A protocol is a set of rules that govern data communications. It represents an agreement between the communicating devices.

Computer Network:

A computer network is a group of computer systems and other computing hardware devices that are linked together through communication channels to facilitate communication and resource-sharing among a wide range of users. Networks are commonly categorized based on their characteristics.

Networks are used to:

• Facilitate communication via email, video conferencing, instant messaging, etc.
• Enable multiple users to share a single hardware device like a printer or scanner.
• Enable file sharing across the network
• Allow for the sharing of software or operating programs on remote systems.
• Make information easier to access and maintain among network users.

Network Criteria:

A network must be able to meet a certain number of criteria. The most important of these ara performance, reliability, and security.

Performance: Performance can be measured in many ways, including transit time and response time. Transit time is the amount of time required for a message to travel from one device to another. Response time is the elapsed time between an inquiry and a response. The Performance of a network depends on a number of factors, including the number of users, the type of transmission medium, the capabilities of the connected hardware, and the efficiency of the software.

Reliability: Network reliability is measured by the frequency of failure, the time it takes a link to recover from a failure, and the network's robustness in a catastrophe.

Security: Network security issues include protecting data from unauthorized access, protecting data from damage and development, and implementing policies and procedures for recovery from breaches and data losses.

Advantages and disadvantages of Networks Advantages

• Sharing devices such as printers saves money.
• Site (software) licences are likely to be cheaper than buying several standalone licences.
• Files can easily be shared between users.
• Network users can communicate by email and instant messenger.
• Security is good - users cannot see other users' files unlike on stand-alone machines.
• Data is easy to backup as all the data is stored on the file server.

Disadvantages:

• Purchasing the network cabling and file servers can be expensive.
• Managing a large network is complicated, requires training and a network manager usually needs to be employed. 
• If the file server breaks down the files on the file server become inaccessible. Email might still work if it ison a separate server. The computers can still be used but are isolated. 
• Viruses can spread to other computers throughout a computer network. 
• There is a danger of hacking, particularly with wide area networks. Security procedures are needed to prevent such abuse, eg a firewall.

Communication Systems:

The communication system is a system which describes the information exchange between two points. The process of transmission and reception of information is called communication. The major elements of communication are the Transmitter of information, Channel or medium of communication and the Receiver of information.

Types Of Communication System Depending on Signal specification or technology, the communication system is classified as follows:

Analog: Analog technology communicates data as electronic signals of varying frequency or amplitude. Broadcast And telephone transmission are common examples of Analog technology.

Digital: Digital technology, the data are generated and processed in two states: High (represented as 1) and Low(represented as 0). Digital technology stores and transmits data in the form of 1s and 0s.

Elements Of Communication Systems:

The definitions of the terms used in the communication system are discussed below. Information Message or information is the entity that is to be transmitted. It can be in the form of audio, video, temperature,picture, pressure, etc.

Signal: The single-valued function of time that carries the information. The information is converted into an electrical form for transmission.

Transducer: A device or an arrangement that converts one form of energy to the other. An electrical transducer convert physical variables such as pressure, force, temperature into corresponding electrical signal variations. Example:

Microphone – converts audio signals into electrical signals.

Photodetector – converts light signals into electrical signals.

Amplifier - The electronic circuit or device that increases the amplitude or the strength of the transmitted signal is called an amplifier.

When the signal strength becomes less than the required value, amplification can be done anywhere inbetween transmitter and receiver. A DC power source will provide for the amplification.

Modulator: As the original message signal cannot be transmitted over a large distance because of their low frequency and amplitude, they are superimposed with high frequency and amplitude wave called carrier wave. This phenomenon of superimposing of message signal with a carrier wave is called modulation. And the resultant wave is modulated wave which is to be transmitted.

Transmitter:It is the arrangement that processes the message signal into a suitable form for transmission and subsequently reception.

Antenna:An Antenna is a structure or a device that will radiate and receive electromagnetic waves. So, they are used in both transmitters and receivers. An antenna is basically a metallic object, often a collection of wires. The Electromagnetic waves are polarised according to the position of the antenna.

Channel:A channel refers to a physical medium such as wire, cables, space through which the signal is passed from the transmitter to the receiver. There are many channel impairments that affect channel performance to a pronounced level. Noise, Attenuation and distortion to mention the major impairments.

Noise :- Noise is one of the channel imperfection or impairment in the received signal at the destination. There are external and internal sources that cause noise. External sources include interference, i.e. interference from nearby transmitted signals (cross talk), interference generated by a natural source such as lightning, solar or cosmic radiation, automobile generated radiation, etc.

Attenuation :- Attenuation is a problem caused by the medium. When the signal is propagating for a longer distance through medium, depending on the length of the medium the initial power decreases. The loss in initial power is directly proportional to the length of the medium. Using amplifiers, the signal power is strengthened or amplified so as to reduce attenuation. Also, digital signals are comparatively less prone to attenuation than analogue signals.

Distortion :- It is also another type of channel problem. When the signal is distorted, the distorted signal may have frequency and bandwidth different from the transmitted signal. The variation in the signal frequency can be linear nonlinear. Receiver arrangement that extracts the message or information from the transmitted signal at the output end of the channel and reproduces it in a suitable form as the original message signal is a receiver.

Demodulator It is the inverse phenomenon of modulation. The process of separation of message signal from the carrier wave takes place in the demodulator. The information is retrieved from the modulated wave.

Repeaters Repeaters are placed at different locations in between the transmitter and receiver. A repeater receives the transmitted signal, amplifies it and send it to the next repeater without distorting the original signal.

Transmission Modes:

The direction in which data can be transmitted between any two linked devices is of three types:

● Simplex

● Half-duplex

● Full- duplex, or duplex.

In simplex mode the data transmits in one direction only, from one system to another system. The sender device that sends data can only send data and cannot receive it. On the other hand the receiver device can only receive the data and cannot send it.Television is an example of simplex mode transmission as the broadcast sends signals to our TV but never receives signals back from our TV. This is a unidirectional transmission.

In half-duplex mode the communication between sender and receiver occurs in both directions, but only one at a time. The sender and receiver can both send and receive the information, but only one is allowed to send at any given time. For example, in walkie-talkies, the speakers at both ends can speak, but they have to speak one by one. They cannot speak simultaneously.

In full duplex transmission mode, the communication between sender and receiver can occur simultaneously. The sender and receiver can both transmit and receive at the same time. For example, in telephone conversation, two people communicate, and both are free to speak and listen at the same time.

Network Types:

A computer network is a group of computers linked to each other through a transmission medium that enables the computer to communicate with another computer and share their resources, data, andapplications.There are mainly three types of computer networks based on their size:

• Local Area Network (LAN)
• Metropolitan Area Network (MAN)
• Wide area network (WAN)

Local Area Network (LAN):

• A local area network (LAN) is a network that connects computers and devices in a limited geographical area such as home, school, computer laboratory, office building, or closely positioned group of buildings. 
• LAN’s enable the sharing of resources such as files or hardware devices that may be needed by multiple users. 
• It is limited in size, typically spanning a few hundred meters, and no more than a mile. 
• It is fast, with speeds from 10 Mbps to 100 Mbps. 
• LAN’s can be either wired or wireless. Twisted pair, coax or fibre optic cable can be used in wiredLAN’s.
• Nodes in a LAN are linked together with a certain topology. These topologies include: Bus ,Ring &Star

Metropolitan Area Network (MAN):

• A metropolitan area network (MAN) is a large computer network that usually spans a city or a large campus.
• A MAN is optimized for a larger geographical area than a LAN, ranging from several blocks of buildings to entire cities. 
• A MAN might be owned and operated by a single organization, but it usually will be used by many individuals and organizations. 
• A MAN often acts as a high speed network to allow sharing of regional resources. 
• Examples of MAN: Telephone company network that provides a high speed DSL to customers and cable TV network.

Wide area network (WAN): 

• WAN covers a large geographic area such as country, continent or even whole of the world. 
• A WAN is two or more LANs connected together. The LANs can be many miles apart. 
• To cover great distances, WANs may transmit data over leased high-speed phone lines or wireless links such as satellites. 
• Multiple LANs can be connected together using devices such as bridges, routers, or gateways, which enable them to share data. 
• The world's most popular WAN is the Internet.

Data Transmission Media:

A transmission medium can be broadly defined as anything that can carry information from a source to destination. The transmission medium is usually free space, metallic cable, or fiber-optic cable.

Transmission media can be generally categorized as either unguided or guided.

Guided Media: In the guided media, the data signals are sent along a specific path, through a wire or a cable. Copper wire and optical fibers are the most commonly used guided media that transmits data as electric signals.Copper wires offer low resistance to current signals, facilitating signals to travel longer distances.Types of guided media:

• Twisted Pair
• Coaxial Pair
• Optical fiber

Twisted Pair:A twisted pair consists of two conductors (normally copper), each with its own plastic insulation, twisted together.

• One of the wires is used to carry signals to the receiver, and the other is used only as a ground reference.
• Twisting tends to decrease the crosstalk.
• Crosstalk is the interference due to the magnetic field of 2 wires nearby.
• Used to transmit both analog and digital Transmission

The two basic types of twisted-pair transmission lines specified are unshielded twisted pair (UTP) and shielded twisted pair (STP).

Shielded Twisted Pair (STP): STP cable has an extra layer of metal foil between the twisted pair of copper wires and the outer covering.The metal foil covering provides additional protection from external disturbances. However, the covering increases the resistance to the signal and thus decreases the length of the cable. STP is costly and is generally used in networks where cables pass closer to devices that cause external disturbances.10 to 100Mbps

Unshielded Twisted Pair (UTP): UTP is the most commonly used medium for transmission over short distances up to 100m. UTP cables ara mostly used for LAN networks. They can be used for voice, low-speed data, high-speed data, audio and paging systems, and building automation and control systems.

Coaxial cable:

• Coaxial cable is very commonly used transmission media, for example, TV wire is usually a coaxial cable. 
• The name of the cable is coaxial as it contains two conductors parallel to each other.
• It has a higher frequency as compared to Twisted pair cable. 
• The inner conductor of the coaxial cable is made up of copper, and the outer conductor is made up of copper mesh.
• The middle core is responsible for the data transferring whereas the copper mesh prevents from the EMI(Electromagnetic interference).

Fiber Optic Cable: A fiber-optic cable is made of glass or plastic and transmits signals in the form of light. Optical fibers are being used for transmission of information over large distances more cost effectively than the copper wire connection. Communication systems are now unthinkable without fiber optics.An optical fiber cable consists of 

• Core - optical fiber conductor (glass) that transmits light, 
• Cladding - an optical material that surrounds the core to prevent any light from escaping the core,and 
• Jacket - outer covering made of plastic to protect the fiber from damage.

Network Topology: Network topology refers to the layout of connected devices, i.e. how the computers, cables, and other components within a data communications network are interconnected, both physically and logically. The physical topology describes how the network is actually laid out, and the logical topology describes how the data actually flow through the network.The topologies commonly used are:-

Bus topology, Star topology, and Ring topology.

Other topologies are Tree Topology, Mesh topology and Hybrid topology.

Bus Topology: 

• Each machine is connected to a single cable.
• Each computer or server is connected to the single bus cable through some kind of connector. 
• A signal from the source travels in both directions to all machines connected on the bus cable until it finds the address on the network that is the intended recipient. 
• If the machine address does not match the intended address for the data, the machine ignores the data. 
• Alternatively, if the data does match the machine address, the data is accepted.

Advantages: 

• If any node or cable (except backbone) fails, it does not affect the whole network. 
• They are relatively cheap and easy to install. 
• Don't require much cabling. 
• Easy to add and remove any node or cable except the backbone cable.

Disadvantages:

• If the backbone cable fails, the entire network goes down. 
• Since all the data are transmitted through the backbone cable, data traffic is high. 
• Bus networks work best with a limited number of devices

Star Topology:

• Each machine is connected to a central hub or switch. 
• It allows each machine on the network to have a point to point connection to the central hub.
• All of the traffic which transverses the network passes through the central hub. 
• The hub acts as a signal booster or repeater which in turn allows the signal to travel greater distances. 
• Hub is the single point of failure.

Advantages: 

• A failure in any node or cable will only take down one computer's network access and not the entire LAN. 
• Easy to diagnose the fault. 
• Easy to add and remove a node or cable.

Disadvantages: 

• Compared to the bus topology, a star network generally requires more cable. 
• If the hub fails, the entire network also fails 
• More expensive than linear bus topology due to the value of the connecting devices (network switches)

Ring Topology:

• Each computer is connected to the network in a closed loop or ring. 
• Each machine or computer has a unique address that is used for identification purposes. 
• The signal passes through each machine or computer connected to the ring in one direction. 
• Ring topologies typically utilize a token passing scheme, used to control access to the network. 
• By utilizing this scheme, only one machine can transmit on the network at a time. 
• A number of repeaters are used for Ring topology with a large number of nodes to send data and to prevent data loss repeaters are used in this network.

Advantages:

• In this data flows in one direction which reduces the chance of packet collisions. 
• It is cheap to install and expand.D
• Due to the presence of token passing the performance of ring topology becomes better than bus topology under heavy traffic. 
• Equal access to the resources.

Disadvantages: 

• Due to the Unidirectional Ring, a data packet (token) must have to pass through all the nodes. 
• If one workstation shuts down, it affects whole network or if a node goes down entire network goes down. 
• Addition and removal of any node during a network is difficult and may cause issue in network activity.

IP address:

In order to understand subnets, we must quickly define IP addresses. Every device that connects to the Internet is assigned a Unique (Internet Protocol) address, enabling data sent over the Internet to reach the right device out of the billions of devices connected to the Internet. While computers read IP addresses as binary code (a series of 1s and 0s), IP addresses are usually written as a series of alphanumeric characters. Eg:- 192.168.10.6

What do the different parts of an IP address mean?This section focuses on IPv4 addresses, which are presented in the form of four decimal numbers separated by periods, like 203.0.113.112. (IPv6 addresses are longer and use letters as well as numbers.)

Every IP address has two parts.

• The first part indicates which network the address belongs to.
• The second part specifies the device within that network.

However, the length of the "first part" changes depending on the network's class.Networks are categorized into different classes, labeled A through E. Class A networks can connect millions of devices. Class B networks and Class C networks are progressively smaller in size. (Class D and Class E networks are not commonly used.)

Let's break down how these classes affect IP address construction:

Class A network (0-128): Everything before the first period indicates the network, and everything after it specifies the device within that network. Using 125.0.113.112 as an example, the network is indicated by "125" and the device by "0.113.112."

Class B network (128-191): Everything before the second period indicates the network. Again using 183.0.113.112 as an example,"203.0" indicates the network and "113.112" indicates the device within that network.

Class C network (192-233): For Class C networks, everything before the third period indicates the network. Using the example(,192.3.0.45), "192.3.0" indicates the Class C network, and "112" indicates the device.

Class D, which covers the 224.0.0.0-239.255.255.255 IP address range, is reserved for multicasting, and class E(240.0.0.0-255.255.255.255) is reserved for “future use.”

MAC Address: 

• MAC address is the physical address, which uniquely identifies each device on a given network. To make communication between two networked devices, we need two addresses: IP address and MAC address. It is assigned to the NIC (Network Interface card) of each device that can be connected to the internet. 
• It stands for Media Access Control, and also known as Physical address, hardware address, or BIA (Burned Address). 
• It is globally unique; it means two devices cannot have the same MAC address. It is represented in a hexadecimal format on each device, such as 00:0a:95:9d:67:16. 
• It is 12-digit, and 48 bits long, out of which the first 24 bits are used for OUI(Organization Unique Identifier), and 24bits are for NIC/vendor-specific. 
• It works on the data link layer of the OSI model. 
• It is provided by the device's vendor at the time of manufacturing and embedded in its NIC, which is ideally cannot be changed.

Internet :

The network formed by the co-operative interconnection of millions of computers, linked together is called Internet.

Intranet :

It is an internal private network built within an organization using Internet and World Wide Web standards and products that allows employees of an organization to gain access to corporate information.

Extranet : It is the type of network that allows users from outside to access the Intranet of an organization.Subnet (sub network) Every website needs a unique IP address, in order to uniquely identify the website, we are dividing the IP network into two or more networks called subnet, which is preferred to control network traffic. 

Packet tracer: Packet tracer is a tool built by Cisco System. It can be used to create complicated network typologies, as well as to test and simulate abstract networking concepts. It acts as a playground for you to explore networking and the experience is very close to what you see in computer networks. Packet Tracer allows users to drag and drop routers, switches, another network devices to create simulated network topologies.

Network devices: Network devices, or networking hardware, are physical devices that are required for communication and interaction between hardware on a computer network.

Hub: Hubs connect multiple computer networking devices together. A hub also acts as a repeater in that it amplifies signals that deteriorate after traveling long distances over connecting cables. A hub is the simplest in the family of network connecting devices because it connects LAN components with identical protocols. Hubs do not perform packet filtering or addressing functions; they just send data packets to all connected devices.

Switch: Switches generally have a more intelligent role than hubs. A switch is a multiport device that improves network efficiency.The switch maintains limited routing information about nodes in the internal network, and it allows connections to systems like hubs or routers. LANs are usually connected using switches. Generally, switches can read the hardware addresses incoming packets to transmit them to the appropriate destination.

Router: A router is a network layer hardware device that transmits data from one LAN to another if both networks support the same set of protocols. So a router is typically connected to at least two LANs and the internet service provider (ISP). It Receives its data in the form of packets, which are data frames with their destination address added. Router also strength send the signals before transmitting them. That is why it is also called repeater.. Most routers can be configured to operate as packet-filtering firewalls.

Bridge: Bridges are used to connect two or more hosts or network segments together. The basic role of bridges in network architecture is storing and forwarding frames between the different segments that the bridge connects. They use hardware Media Access Control (MAC) addresses for transferring frames. By looking at the MAC address of the devices connected to each segment, bridges can forward the data or block it from crossing. Bridges can also be used to connect two physical LANs into a larger logical LAN.

Gateway: Gateways normally work at the Transport and Session layers of the OSI model. At the Transport layer and above, there are numerous protocols and standards from different vendors; gateways are used to deal with them. Gateways provide translation between networking technologies such as Open System Interconnection (OSI) and Transmission Control Protocol/Internet Protocol (TCP/IP). Gateways perform all of the functions of routers and more. In fact, a router with added translation functionality is a gateway.

Modem: Modems (modulators-demodulators) are used to transmit digital signals over analog telephone lines. Thus, digital signals are converted by the modem into analog signals of different frequencies and transmitted to a modem at the receiving location. The receiving modem performs the reverse transformation and provides a digital output to a device connected toa modem, usually a computer.

NIC: Network interface card (NIC) is a hardware component used by computers to connect to Ethernet LAN and communicate with other devices on the LAN. The earliest Ethernet cards were external to the system and needed to be installed manually. In modern computer systems, it is an internal hardware component. The NIC has RJ45 socket where network cable is physically plugged in.OSI (Open System Interconnection)

Model: The Open Systems Interconnection (OSI) model describes seven layers that computer systems use to communicate overa network. It was the first standard model for network communications, adopted by all major computer and telecommunication companies in the early 1980s.The modern Internet is not based on OSI, but on the simpler TCP/IP model. However, the OSI 7-layer model is still widely used, as it helps visualize and communicate how networks operate, and helps isolate and troubleshoot networkingproblems.OSI was introduced in 1983 by representatives of the major computer and telecom companies, and was adopted by Isaac an international standard in 1984.These are the seven layers of the OSI model − 

• Application layer:The application layer is used by end-user software such as web browsers and email clients. It provides protocols that allow software to send and receive information and present meaningful data to users. A few examples application layer protocols are the Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP), Post Office Protocol (POP), Simple Mail Transfer Protocol (SMTP), Browsers, Skype Messenger.
• Presentation layer:The presentation layer prepares data for the application layer. It defines how two devices should encode, encrypt,and compress data so it is received correctly on the other end. The presentation layer takes any data transmitted bythe application layer and prepares it for transmission over the session layer. 
• Session layer:The session layer creates communication channels, called sessions, between devices. It is responsible for opening sessions, ensuring they remain open and functional while data is being transferred, and closing them when communication ends. The session layer can also set checkpoints during a data transfer—if the session is interrupted, devices can resume data transfer from the last checkpoint. All the above 3 layers(including Session Layer) are integrated as a single layer in the TCP/IP model as “Application Layer”. Gateways. 
• Transport layer:The transport layer takes data transferred in the session layer and breaks it into “segments” on the transmitting end. It is responsible for reassembling the segments on the receiving end, turning it back into data that can be used by the session layer. The transport layer carries out flow control, sending data at a rate that matches the connection speed of the receiving device, and error control, checking if data was received incorrectly and if not, requesting it again. Operating System, Firewall. 
• Network layer:The network layer has two main functions. One is breaking up segments into network packets, and reassembling the packets on the receiving end. The other is routing packets by discovering the best path across a physical network. The network layer uses network addresses (typically Internet Protocol addresses) to route packets to destination node. Routers. 
• Data Link layer:The data link layer establishes and terminates a connection between two physically-connected nodes on a network.It breaks up packets into frames and sends them from source to destination. This layer is composed of two parts—Logical Link Control (LLC), which identifies network protocols, performs error checking and synchronised, and Media Access Control (MAC) which uses MAC addresses to connect devices and define permission to transmit and receive data. Switch & Bridge. 
• Physical layer:The physical layer is responsible for the physical cable or wireless connection between network nodes. It defines the connector, the electrical cable or wireless technology connecting the devices, and is responsible for transmission of the raw data, which is simply a series of 0s and 1s, while taking care of bit rate control. Hub,Repeater, Modem, Cables are Physical Layer devices.

Protocols:

TCP/IPTCP/IP stands for Transmission Control Protocol/Internet Protocol. TCP/IP is a set of layered protocol used for communication over the Internet. The communication model of this suite is client-server model. A Computer that sends a request is the client and a computer to which the request is sent is the server.

FTPAs we have seen, the need for network came up primarily to facilitate sharing of files between researchers.And to this day, file transfer remains one of the most used facilities.The protocol that handles these requests is File Transfer Protocol or FTP.

SMTP: SMTP stands for Simple Mail Transfer Protocol. It is connection oriented application layer protocol that is widely used to send and receive email messages. It was introduced in 1982 by RFC 821 and last updated 2008 by RFC 5321. The updated version is most widely used email protocol.Mail servers and mail transfer agents use SMTP to both send and receive messages. However, user level applications use it only for sending messages. For retrieving they use IMAP or POP3 because they provide mailbox management.

POP3 or Post Office Protocol Version 3 is an application layer protocol used by email clients to retrieve email messages from mail servers over TCP/IP network. POP was designed to move the messages from server to local disk but version 3 has the option of leaving a copy on the server.

FTP: 

• FTP stands for File transfer protocol. 
• FTP is a standard internet protocol provided by TCP/IP used for transmitting the files from one host to another. 
• It is mainly used for transferring the web page files from their creator to the computer that acts as aserver for other computers on the internet. 
• It is also used for downloading the files to computer from other servers.

HTTP: 

• HTTP stands for HyperText Transfer Protocol. 
• It is a protocol used to access the data on the World Wide Web (www). 
• The HTTP protocol can be used to transfer the data in the form of plain text, hypertext, audio, video,and so on. 
• This protocol is known as HyperText Transfer Protocol because of its efficiency that allows us to using a hypertext environment where there are rapid jumps from one document to another document.

Unguided media: 

• An unguided transmission transmits the electromagnetic waves without using any physical medium.Therefore it is also known as wireless transmission. 
• In unguided media, air is the media through which the electromagnetic energy can flow easily.

Radio waves:

• Radio waves are the electromagnetic waves that are transmitted in all the directions of free space.
• Radio waves are omnidirectional, i.e., the signals are propagated in all the directions.
• The range in frequencies of radio waves is from 3 Khz to 1 khz.
• In the case of radio waves, the sending and receiving antenna are not aligned, i.e., the wave sent by the sending antenna can be received by any receiving antenna.
• An example of the radio wave is FM radio.

Microwaves:

• Terrestrial Microwave transmission is a technology that transmits the focused beam of a radio signal from one ground-based microwave transmission antenna to another.
• Microwaves are the electromagnetic waves having the frequency in the range from 1GHz to 1000 GHz.
• Microwaves are unidirectional as the sending and receiving antenna is to be aligned, i.e., the waves sent bythe sending antenna are narrowly focussed
• In this case, antennas are mounted on the towers to send a beam to another antenna which is km away.
•  It works on the line of sight transmission, i.e., the antennas mounted on the towers are the direct sight of each other.
• An example of the microwave is sensor system.

Infrared:

• An infrared transmission is a wireless technology used for communication over short ranges.
• The frequency of the infrared in the range from 300 GHz to 400 THz.
• It is used for short-range communication such as data transfer between two cell phones, TV remote operation, data transfer between a computer and cell phone resides in the same closed area.