Wireless Media

Wireless Media:

Wireless telecommunications, is the transfer of information between two or more points that are physically not connected. Distances can be short, as a few meters as in television remote control; or long
ranging from thousands to millions of kilometers for deep‐space radio communications. It encompasses
various types of fixed, mobile, and portable two‐way radios, cellular telephones, personal digital
assistants (PDAs), and wireless networking. Other examples of wireless technology include GPS units, garage door openers and or garage doors, wireless computer mice, keyboards and headsets, satellite television and cordless telephones.
         Network Connecting Device Network Connecting Device: (Modem, NIC, Switch / Hub, Router,
Gateway,
Repeater, Bluetooth, IR, WiFi):

Computer networking devices are units that mediate data in a computer network. Computer networking devices are also called network equipment, Intermediate Systems (IS) or InterWorking Unit (IWU). Units which are the last receiver or generate data are called hosts or data terminal equipment.

Modem
A modem (modulator‐demodulator) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog signals, from light emitting diodes to radio.
      The most familiar example is a voice band modem that turns the digital data of a personal computer into modulated electrical signals in the voice frequency range of a telephone channel. These signals can be transmitted over telephone lines and demodulated by another modem at the receiver side to recover the digital data.
Modems are generally classified by the amount of data they can send in a given unit of time, usually
expressed in bits per second (bit/s, or bps). Modems can alternatively be classified by their symbol rate,
measured in baud. The baud unit denotes symbols per second, or the number of times per second the
modem sends a new signal. For example, the ITU V.21 standard used audio frequency‐shift keying, that
is to say, tones of different frequencies, with two possible frequencies corresponding to two distinct symbols (or one bit per symbol), to carry 300 bits per second using 300 baud. By contrast, the original ITU V.22 standard, which was able to transmit and receive four distinct symbols (two bits per symbol), handled 1,200 bit/s by sending 600 symbols per second (600 baud) using phase shift keying.

Network interface controller(NIC)

A network interface controller (also known as a network interface card, network adapter, LAN adapter
and by similar terms) is a computer hardware component that connects a computer to a computernetwork.
Whereas network interface controllers were commonly implemented on expansion cards that plug intoa computer bus, the low cost and ubiquity of the Ethernet standard means that most newer computershave a network interface built into the motherboard.
The network controller implements the electronic circuitry required to communicate using a specific
physical layer and data link layer standard such as Ethernet, Wi‐Fi, or Token Ring. This provides a base
for a full network protocol stack, allowing communication among small groups of computers on the
same LAN and large‐scale network communications through routable protocols, such as IP.

Switch / Hub

A network switch or switching hub is a computer networking device that connects network segments.
The term commonly refers to a multi‐port network bridge that processes and routes data at the datalink layer (layer 2) of the OSI model. Switches that additionally process data at the network layer (Layer3) and above are often referred to as Layer 3 switches or multilayer switches.
         The network switch plays an integral part in most modern Ethernet local area networks (LANs). Mid‐to‐large sized LANs contain a number of linked managed switches. Small office/home office (SOHO)applications typically use a single switch, or an all‐purpose converged device such as a gateway to accesssmall office/home broadband services such as DSL or cable internet. In most of these cases, the end‐user device contains a router and components that interface to the particular physical broadbandtechnology. User devices may also include a telephone interface for VoIP.An Ethernet switch operates at the data link layer of the OSI model to create a separate collision domainfor each switch port. With 4 computers (e.g., A, B, C, and D) on 4 switch ports, A and B can transfer databack and forth, while C and D also do so simultaneously, and the two conversations will not interfere
with one another. In the case of a hub, they would all share the bandwidth and run in half duplex,
resulting in collisions, which would then necessitate retransmissions. Using a switch is called microsegmentation. This allows computers to have dedicated bandwidth on a point‐to‐point
connections to the network and to therefore run in full duplex without collisions.

Router

A router is a device that forwards data packets between telecommunications networks, creating anoverlay internetwork. A router is connected to two or more data lines from different networks. Whendata comes in on one of the lines, the router reads the address information in the packet to determineits ultimate destination. Then, using information in its routing table or routing policy, it directs thepacket to the next network on its journey or drops the packet. A data packet is typically forwarded fromone router to another through networks that constitute the internetwork until it gets to its destination

node.The most familiar type of routers are home and small office routers that simply pass data, such as webpages and email, between the home computers and the owner's cable or DSL modem, which connectsto the Internet (ISP). However more sophisticated routers range from enterprise routers, which connectlarge business or ISP networks up to the powerful core routers that forward data at high speed along theoptical fiber lines of the Internet backbone.

Gateway

A network gateway is an internetworking system capable of joining together two networks that usedifferent base protocols. A network gateway can be implemented completely in software, completely in
hardware, or as a combination of both. Depending on the types of protocols they support, network
gateways can operate at any level of the OSI model.  Because a network gateway, by definition, appears at the edge of a network, related capabilities likefirewalls tend to be integrated with it. On home networks, a broadband router typically serves as thenetwork gateway although ordinary computers can also be configured to perform equivalent functions.  

Bluetooth:

Bluetooth is a wireless technology standard for exchanging data over short distances from fixed and mobile devices. Bluetooth is used to create personal area networks (PANs) with high levels of security. Bluetooth Was created by telecoms vendor Ericsson in 1994.

Infrared 

Infrared (IR) light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.7 micrometers, and extending conventionally to 300 micrometres. These wavelengths correspond to a frequency range of approximately 1 to 430 THz,and include most of the thermal radiation emitted by objects near room temperature.   Microscopically,
IR light is typically emitted or absorbed by molecules when they change their rotational‐vibrational
movements.Sunlight at zenith provides an irradiance of just over 1 kilowatt per square meter at sea level. Of thisenergy, 527 watts is infrared radiation, 445 watts is visible light, and 32 watts is ultraviolet radiation.  

WiFi

Wi‐Fi is a wireless standard for connecting electronic devices. The fullform of wifi is "wireless feidelity". A Wi‐Fi enabled device such as a personalcomputer, video game console, smartphone, and digital audio player can connect to the Internet whenwithin range of a wireless network connected to the Internet. A single access point (or hotspot) has arange of about 20 meters indoors. Wi‐Fi has a greater range outdoors and multiple overlapping accesspoints can cover large areas.

        "Wi‐Fi" is a trademark of the Wi‐Fi Alliance and the term was originally created as a simpler name forthe "IEEE 802.11" standard. Wi‐Fi is used by over 700 million people, there are over 4 million hotspots
(places with Wi‐Fi Internet connectivity) around the world, and about 800 million new Wi‐Fi devices
every year.[citation needed] Wi‐Fi products that complete the Wi‐Fi Alliance interoperability
certification testing successfully can use the Wi‐Fi CERTIFIED designation and trademark.