Wireless Communication

Wireless Computing

In this video we're going to review the different wireless technologiesas an introduction to the module. Wireless communications use wavesas transmission medium. Depending on the frequency, we'llfind technologies based on light or on conventional radio waves,that's because light it's really a very high frequency electromagneticradiowave. We will start with light, we will start with infrared thatare light-based communication in which infrared beams are use astransmission medium for short distances.Infrared are known visible light waves that are a little underred in the radio frequency spectrum. You can findthem in, for example, in tv remotes and in some data links,but for most personal data transmission they have been replacedby bluetooth because it is more convenient.You can also find visible light communications equipment that'sfree space optical communications equipment that relyon leds or lasers and they can achieve gigabit per second speedsup to a couple of kilometers, so to link two buildings if youcannot put a cable or is it difficult you can use one of thesetwo technologies to connect with a high speed linkone with the other. So now we are going speak, we are going to go from lightto radio waves, because bluetooth is a  short rangeconnection method that is based on radio waves.It's used to connect devices like headphones or speakersor for short distance data transmission.Wi-Fi is really a trademark but is used to refer to wirelesslocal area networks based on radio waves.Nowadays these are the most popular connectionswith mobile devices if you are in a range of tens of metersfrom a WI-Fi access point because you can connect to internetfor free or for a much lower fee than usingthe cellular network that the phone has. Andthis the network we're going the speak about now: mobile broadband is thename use for the connection to cell phone towers and its use tocreate remote connections through wireless internet serviceproviders, so it's data connections using your mobile phone.It allows near ubiquitous access to the Internetand the users can be up to some kilometers or milesfrom base station to connect with it.Another technology that is very important is microwave links thatare used for point to point connections.They redirect the beam from the transmitting and antenna to the receivingantenna and minimize interferences withother equipment. And finally we're going to speak about satellites thatare used by telecommunication companies to cover large distancesand connect areas with difficult access. You can finda satellite phone that you can use in the middle of the desert.Satellites are quite far so, depending on the application andon the bandwith or whatever you need,the users may need to use large antennas or high power devices.And to finish the video i'm going to speak about the spectrumand how government agencies need toallot it, because there are a lot of uses and to avoid interferencesa careful distribution of frequenciesused for different applications is needed.You have to tell if you're gonna use frequencies for data orfor television or for radio or for cellular phones.Now they are... so yo have to allot part of thespectrum for that, and now they are in the process ofchanging some frequencies from televisionto cell phones because they need more for cell phones.So all these is done by government agenciesthat dictate how the radio spectrum is going to be used andthey are coordinated in an international body so there are nodifferences between a differentcountries

InfraRed
Hi , in this video we will explain how machines communicate using infrared light.So infrared light is actually only one of the availablemethods in free-space optical communications, FSO.So infrared light uses the light as a media to transmitinformation over the air. Morse code, for example, used ona boat or a lighthouse are other examples of FSO (free space optical)communications. Another free-space optical communicationscan use for example led or laser sources for high-speed datalinks. Infrared is used in the remote controls that we use to controlour televisions and you can think yourself about them to discoveradvantages or drawbacks of the specific media.The standards that regulates data transmission using infrared connectionsis defined by the infrared data associationthe irDA. And this irDa is designed for very smalldistances as there may be many other infrared light sources andtransmitters are low power. So light is blocked by any physicaloptic in the way, so you need a direct or reflected path betweenthe transmitter and receiver if you use infraredcommunication. At the beginning infrared was used to create personalarea networks PANs, but the appearance of bluetooth and Wi-fi  hasactually displaced this technology for this use.So then if you use light, visible light is used for a high speeddata communication in the one or two kilometer range.And there are commercial systems that use led or laser sourcesfor that, and they require a line of sight that is able to transmitup to ten gigabytes per seconds,depending on distance and also atmospheric factors,because, rain, fog and dust can cause extreme data rate dropswhen use these types of data transmission.

Bluetooth
In this unit we're gonna speak about bluetooth.Bluetooth uses radio waves to transmit information amongdifferent devices. It is a technology that allows communication at shortdistances, between ten and fifteen meters maximum,that is a little farther than infrared rays.It is usually employed to communicate a computer with someperipherals or to connect different devices among them.For example, for smartphones it is useto connect peripheral devicesor for proximal data transmission as you can see in thescreen or to synchronize with a desktop computer, but thisuse is being replaced by Wifi connectionsin a lot of cases. Another very important use of bluetooth isto link wireless keyboards and pointing deviceswith computers, tablets or even smart tvs,as bluetooth links are the most common technology foundto do this. The ability of bluetooth to interconnect devices and its range,it's short range, makes it the most used technology to createpersonal area networks, that are called PAN.That are networks that are formed by devices around a personor a desktop. For example all these equipment are connectedusing bluetooth. To end with bluetooth, we're going to speak about pairing. Pairing is aconnection process that has to be done oncebefore two bluetooth devices are able to connect.This is needed to enhance privacy and security,so only authorized devices can connect, the process isvery easy. One device has to be setto discoverable mode and then the other devicehas to search for bluetooth available devices, select it and thenprovide the pin password. This is only needed once for each pairof devices. The process is called pairingbut multiple bluetooth devices can be connected at the same timepairing each of them with a main one.