Wireless Communication

Wireless communications is one of the most active areas of technology development of our time. This development is being driven primarily by the transformation of what has been largely a medium for supporting voice telephony into a medium for supporting other services, such as the transmission of video, images, text, and data. Thus, similar to the developments in wireline capacity in the 1990s, the demand for new wireless capacity is growing at a very rapid pace. Although there are, of course, still a great many technical problems to be solved in wireline communications, demands for additional wireline capacity can be fulfilled largely with the addition of new private infrastructure, such as additional optical fiber, routers, switches, and so on. On the other hand, the traditional resources that have been used to add capacity to wireless systems are radio bandwidth and transmitter power. Unfortunately, these two resources are among the most severely limited in the deployment of modern wireless networks: radio bandwidth because of the very tight situation with regard to useful radio spectrum, and transmitter power because mobile and other portable services require the use of battery power, which is limited.

Internet Protocol: FTP, HTTP, HTTPS, TCP/IP

Internet Protocol

(Internet Protocol) is the primary network protocol used on the Internet, developed in the 1970s. On the Internet and many other networks, IP is often used together with the Transport Control Protocol (TCP) and referred to interchangeably as TCP/IP.

IP supports unique addressing for computers on a network. Most networks use the Internet Protocol version 4 (IPv4) standard that features IP addresses four bytes (32 bits) in length. The newer Internet Protocol version 6 (IPv6) standard features addresses 16 bytes (128 bits) in length.

Data on an Internet Protocol network is organized into packets. Each IP packet includes both a header (that specifies source, destination, and other information about the data) and the message data itself.

IP functions at layer 3 of the OSI model. It can therefore run on top of different data link interfaces including Ethernet and Wi-Fi.

FTP

Short for File Transfer Protocol, the protocol for exchanging files over the Internet. FTP works in the same way as HTTP for transferring Web pages from a server to a user's browser and SMTP for transferring electronic mail across the Internet in that, like these technologies, FTP uses the Internet's TCP/IP protocols to enable data transfer.

FTP is most commonly used to download a file from a server using the Internet or to upload a file to a server (e.g., uploading a Web page file to a server).

HTTP

What is HTTP?

HTTP, the Hypertext Transfer Protocol, is the application-level protocol that is used to transfer data on the Web. HTTP comprises the rules by which Web browsers and servers exchange information. Although most people think of HTTP only in the context of the World-Wide Web, it can be, and is, used for other purposes, such as distributed object management systems.

How Does HTTP Work?

HTTP Is a request-response protocol. For example, a Web browser initiates a request to a server, typically by opening a TCP/IP connection. The request itself comprises

• a request line,
• a set of request headers, and
• an entity.

The server sends a response that comprises

• a status line,
• a set of response headers, and
• an entity.

The entity in the request or response can be thought of simply as the payload, which may be binary data. The other items are readable ASCII characters. When the response has been completed, either the browser or the server may terminate the TCP/IP connection, or the browser can send another request.

HTTPS (Secure HTTP)

Hypertext Transfer Protocol Secure (HTTPS) is a widely used communications protocol for secure communication over a computer network, with especially wide deployment on the Internet. Technically, it is not a protocol in itself; rather, it is the result of simply layering the Hypertext Transfer Protocol (HTTP) on top of the SSL/TLS protocol, thus adding the security capabilities of SSL/TLS to standard HTTP communications.

HTTPS is especially important over unencrypted networks such as WiFi as anyone on the same local network can do packet sniffing and discover sensitive information. Additionally, many free to use and even paid for WLAN networks do packet injection for serving their own ads on webpages or just for pranks, however this can be exploited maliciously e.g. by injecting malware and spying on users. Another example where HTTPS is important is connections over Tor (anonymity network), as malicious Tor nodes can damage or alter the contents passing through them in an insecure fashion and inject malware into the connection. This is one reason why EFF and Torproject started the development of HTTPS Everywhere, which is included in the Tor Browser Bundle.which use encryption, can be used to create a secure connection between two machines. The browser uses SSL or TLS when connecting to a secure part of a website indicated by an HTTPS URL, that is, a URL with the prefix https://. The browser then uses HTTP to send and receive requests over this secure connection.

TCP/IP
TCP/IP (Transmission Control Protocol/Internet Protocol) is the basic communication language or protocol of the Internet. It can also be used as a communications protocol in a private network (either an intranet or an extranet). When you are set up with direct access to the Internet, your computer is provided with a copy of the TCP/IP program just as every other computer that you may send messages to or get information from also has a copy of TCP/IP.

TCP/IP is a two-layer program. The higher layer, Transmission Control Protocol, manages the assembling of a message or file into smaller packets that are transmitted over the Internet and received by a TCP layer that reassembles the packets into the original message. The lower layer, Internet Protocol, handles the address part of each packet so that it gets to the right destination. Each gateway computer on the network checks this address to see where to forward the message. Even though some packets from the same message are routed differently than others, they'll be reassembled at the destination.

TCP/IP uses the client/server model of communication in which a computer user (a client) requests and is provided a service (such as sending a Web page) by another computer (a server) in the network. TCP/IP communication is primarily point-to-point, meaning each communication is from one point (or host computer) in the network to another point or host computer. TCP/IP and the higher-level applications that use it are collectively said to be "stateless" because each client request is considered a new request unrelated to any previous one (unlike ordinary phone conversations that require a dedicated connection for the call duration). Being stateless frees network paths so that everyone can use them continuously. (Note that the TCP layer itself is not stateless as far as any one message is concerned. Its connection remains in place until all packets in a message have been received.)

Many Internet users are familiar with the even higher layer application protocols that use TCP/IP to get to the Internet. These include the World Wide Web's Hypertext Transfer Protocol (HTTP), the File Transfer Protocol (FTP), Telnet (Telnet) which lets you logon to remote computers, and the Simple Mail Transfer Protocol (SMTP). These and other protocols are often packaged together with TCP/IP as a "suite."

Personal computer users with an analog phone modem connection to the Internet usually get to the Internet through the Serial Line Internet Protocol (SLIP) or the Point-to-Point Protocol (PPP). These protocols encapsulate the IP packets so that they can be sent over the dial-up phone connection to an access provider's modem.

Protocols related to TCP/IP include the User Datagram Protocol (UDP), which is used instead of TCP for special purposes. Other protocols are used by network host computers for exchanging router information. These include the Internet Control Message Protocol (ICMP), the Interior Gateway Protocol (IGP), the Exterior Gateway Protocol (EGP), and the Border Gateway Protocol (BGP).

Internet Connectivity & its modes

Internet Connectivity

Internet access is the means by which individual terminals, computers, mobile devices, and local area networks are connected to the global Internet. Internet access is usually sold by Internet Service Providers (ISPs) that use many different technologies offering a wide range of data rates to the end user. Consumer use first became popular through dial-up connections in the 1980s and 1990s. By the first decade of the 21st century, many consumers had switched away from dial-up to dedicated connections, most Internet access products were being marketed using the term "broadband", and broadband penetration was being treated as a key economic indicator.

Types or modes of Internet Connections

As technology grows, so does our need for things to go faster. Ten years ago, websites just included images, coloured text and some repetitive melodies. Now Flash websites, animations, high resolution photos, online gaming, videos or streaming ( radio on the internet ), are getting more popular for people who demand faster and faster internet connections.

The connection speeds listed below represent an average speed at the time of publication ( May 2009 ). This will no doubt change over time.

1) PCI modem (Fig.4.1).

Analogue up to 56000 bits per second. It means that in a second, 56000 bits ( 0 or 1 ) travel through the copper wire. It is both economical and slow and it is also called dial-up access. If you connect the modem, you get internet but as it uses the analogue telephone line, if you surf on the internet, nobody can call you because the line is busy.

Using a modem connected to your PC which is very cheap ( about 10 €) , users connect to the Internet only if you click on the telephone Access Icon and the computer dials the phone number provided by your ISP ( Internet Service Provider ) and connects to the network. The signal is analogue because data is sent over an analogue telephone network. This modem converts

received analogue data to digital ( always analogue on the telephone site and digital on the computer side ).

As dial-up access uses ordinary telephone lines the data rates are limited and the quality of the connection is not always good. Nowadays very few people use this type of connection.

2) DSL:

DSL or - an 'always on' connection- uses the existing 2-wire copper telephone line connected to the internet and won't tie up  your phone like the old modem does. There is no need to dial-in to your ISP as DSL is always on. DSL is called ADSL ( Short for Asymmetric Digital Subscriber Line) for home subscribers.

As we said before ADSL is short for asymmetric digital subscriber line and supports data rates up to 10 Mbits ( May 2009 ) when receiving data ( download ) and from 16 to 640 Kbps when sending data ( upload ). ADSL is called asymmetric because it supports different data rates for upload than for download traffic.

3) Cable

There are two type of cable; Coaxial and optical fibre. The first one is used by cable TV and that is common for data communications ( Fig.4.2).

The cross-section of the cable shows a single centre solid wire made of copper surrounded by a copper mesh conductor. Between the main wire ( in the centre ) and the mesh conductor is an insulating dielectric. This dielectric ( blue part in the image ) has a large effect on the essential features of the cable. Depending on the material that insulator is made of, the cable has different inductance and capacitance values and these values affect how quickly data travels through the wire. The last layer is an outside insulator to protect the whole wire.

Data is transmitted through the rigid wire, while the outer copper mesh layer serves as a line to ground.

4) Wireless Internet Connections

Wireless broadband or Wireless Internet Connections. Instead of using cable networks for your Internet connection, WIC uses radio frequency .Wireless Internet can be accessed from anywhere as long as your WIFI adaptor is located  within a network coverage area. It also provides an always-on connection and  it is still considered to be relatively new.

5) Satellite

IoS short for  Internet over Satellite allows a user to access the Internet via a geostationary  satellite that orbits the earth. A geostationary satellite is a type of satellite placed at a fixed position above the earth's surface. Because of the large distances between home and satellite,  signals must travel from the earth up to the satellite and back again. It causes  a slight delay between the request and the answer.

E-mail, Chat, Video Conferencing

E-mail

Short for electronic mail, the transmission of messages over communications networks. The messages can be notes entered from the keyboard or electronic files stored on disk. Most mainframes, minicomputers, and computer networks have an e-mail system. Some electronic-mail systems are confined to a single computer system or network, but others have gateways to other computer systems, enabling users to send electronic mail anywhere in the world. Companies that are fully computerized make extensive use of e-mail because it is fast, flexible, and reliable.

Most e-mail systems include a rudimentary text editor for composing messages, but many allow you to edit your messages using any editor you want. You then send the message to the recipient by specifying the recipient's address. You can also send the same message to several users at once. This is called broadcasting.

Sent messages are stored in electronic mailboxes until the recipient fetches them. To see if you have any mail, you may have to check your electronic mailbox periodically, although many systems alert you when mail is received. After reading your mail, you can store it in a text file, forward it to other users, or delete it. Copies of memos can be printed out on a printer if you want a paper copy.

All online services and Internet Service Providers (ISPs) offer e-mail, and most also support gateways so that you can exchange mail with users of other systems. Usually, it takes only a few seconds or minutes for mail to arrive at its destination. This is a particularly effective way to communicate with a group because you can broadcast a message or document to everyone in the group at once.

Although different e-mail systems use different formats, there are some emerging standards that are making it possible for users on all systems to exchange messages. In the PC world, an important e-mail standard is MAPI. The CCITT standards organization has developed the X.400 standard, which attempts to provide a universal way of addressing messages. To date, though, the de facto addressing standard is the one used by the Internet system because almost all e-mail systems have an Internet gateway.

Another common spelling for e-mail is email.

Chat

Real-time communication between two users via computer. Once a chat has been initiated, either user can enter text by typing on the keyboard and the entered text will appear on the other user's monitor. Most networks and online services offer a chat feature.

Chat in Instant Messaging terms is the ability to open (or start) a conversation with another user or users.

Once such a conversation has been instigated all the members of that conversation are able to communicate (or chat) with each other. Each member of the chat can see what every other member types, and in turn any responses sent will be sent to all other members of the conversation.

Online conversations in which you are immediately able to send messages back and forth to one another is called chat.

Often you'll hear people say, "I was chatting last night to someone from [this state.]" Other times you'll hear them say "I was chatting to someone from [this country.]" Chances are they weren't talking about the telephone, which can cost a few cents every minute. They were probably talking about online chat. Online chat doesn't cost anything extra, as long as you have an Internet connection.

Video Conferencing

Video conferencing is a communications technology that integrates video and audio to connect users anywhere in the world as if they were in the same room. This term usually refers to communication between three or more users who are in at least two locations, rather than one-on-one communication, and it often includes multiple people at each location. Each user or group of users who are participating in a video conference typically must have a computer, a camera, a microphone, a video screen and a sound system. Another requirement is a connection to the communications system that is being used, which in the 21st century usually is the Internet but might also be a satellite-based system, a broadcast signal or other communications technology. When using video conferencing, participants can see and hear each other in real time or close to it, allowing natural face-to-face conversations and visual elements that are not possible with voice-only communications technology.

Uses

This technology is especially popular in the field of business because it allows meetings or conferences to be held without the need for all of the participants to travel to a single location, so it saves time and money. For the same reasons, it also is useful in the fields of academics and medicine. Almost any organization that holds meetings for people from different locations — no matter how far apart they are, whether across town or around the world — can make use of video conferencing.

History

Communications companies have been dabbling in this technology essentially since the invention of television. It was mostly impractical or limited in its use, however, before the advent of broadband Internet. Early devices often suffered from poor picture quality. Videophones, which became available in the 1970s, never became popular because they were quite expensive. With the arrival of broadband Internet in the 1990s, however, users could engage in video conferencing through their home computers simply by buying webcams and the appropriate programs.