CDMA(Coded-Division-Multiple Access)

CDMA is abbreviated as Code-Division Multiple Access refers to any of numerous protocols used in second-generation (2G) and third-generation (3G) wireless communications. CDMA is a form of multiplexing, which allows frequent signals to occupy a single transmission channel, optimizing the use of available bandwidth. The CDMA channel is supposedly 1.23 MHz wide. CDMA minimizes signal breakup as a handset passes from one cell to another. CDMA is compatible with other cellular technologies, this permit for countrywide roaming.

CDMA utilizes analog-to-digital conversion (ADC) in grouping with spread spectrum technology. Audio input is first converted into binary elements. The frequency of the transmitted signal is then made to differ according to a discrete pattern (code), so it can be intercepted only by a receiver whose frequency response is associated with decoder, so it follows exactly along with the transmitter frequency. There are trillions of possible frequency-sequencing codes, which enhance privacy and makes genetic copy difficult. The technology is used in ultra-high-frequency (UHF) cellular telephone systems in the 800-MHz and 1.9-GHz bands.

CDMA is a "spread spectrum" technology; permits many user to occupy the same time and frequency allocations in a given band/space. CDMA (Code Division Multiple Access) assigns sole codes to each communication to discriminate it from others in the identical spectrum. In a world of fixed spectrum resources, CDMA enables many more people to split the airwaves at the same time than do alternative technologies.

There are two main version of it:

1.   CDMA1: Still in use in USA, has transmission speed of only up to 14.4 Kbps in its single channel appearance and up to 115 Kbps in an eight-channel figure.

2.   CDMA 2000: IMT-CDMA Multi-Carrier, wideband that can support mobile data communications at speeds sorting from 144 Kbps to 2 Mbps.

Application Of Technology:

•     Consumer Oriented: Admired consumer claims include short messaging, instant messaging, picture messaging, mobile TV, music downloads, video downloads, online gaming with luxuriantly caused to be 3D graphics, and location-based services.
•     Business: The business client benefits from having high-speed data connectivity to the Internet and their virtual private network (VPN), and services such as sending and receiving e-mail with bulky attachments, push-to-talk and multimedia (PTT and PTM) functions.
•     Public Help: The over services are also valuable gear for the public sector, including national security, first-responder and public safety users. Providing worldwide access to telephony and Internet services is a key economic priority for most governments. Forward looking governments are taking full benefit of these services by connecting schools, hospitals, medical clinics, police stations and communities to CDMA2000 telecommunication networks........ to be cont...

Satellite

A satellite is such an object which has been placed into earth's orbit by human endeavour. Such objects are called artificial satellites to differentiate them from natural satellites like the Moon.Satellites are used for a large number of reasons. Most useful types include military and civilian Earth observation satellites, communications satellites, navigational satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites. Satellite orbits vary greatly, depending on the purpose of the satellite, and are classified in a number of ways.

             Well-known classes include low Earth orbit, polar orbit, and geostationary orbit.

There are two types of satellites:

1. Natural
2. Artificial

Natural Satellites are:

Types of Satellite (Artificial) and their works are:

• Anti-Satellite weapons or "Killer Satellites" are satellites that are designed to destroy enemy warheads, satellites, other space assets.
• Astronomical Satellites are satellites used for observation of distant planets, galaxies, and other outer space objects.
• Bio-satellites are satellites designed to carry living organisms, generally for scientific and Engineering experimentation .
• Communications satellites are satellites located in space for the purpose of telecommunications. Modern communications satellites typically use geosynchronous orbits or Low Earth orbits.
• Miniaturized satellites are satellites of unusually have low masses and small sizes.
• Navigational satellites are satellites which use radio time signals transmitted to enable mobile receivers on the ground to determine their exact location.
• Reconnaissance satellites are Earth observation satellite or communications satellite deployed for military or intelligence applications. Very little is known about the full power of these satellites, as governments who operate them usually keep information pertaining to their reconnaissance satellites classified.
• Earth observation satellites are satellites intended for non-military uses such as environmental monitoring, meteorology, map making.
• Tether satellites are satellites which are connected to another satellite by a thin cable called a tether.
• Weather satellites are primarily used to monitor Earth's weather and climate with environmental change.
• Recovery satellites are satellites that provides a recovery of reconnaissance, biological, space-production and other payloads from orbit to Earth.
• Manned spacecraft (spaceships) are large satellites able for put human into an orbit, being on it and recovery back to Earth. Spacecrafts, and orbital parts-spaceplanes of reusable systems also, has a major propulsion or landing facilities, and often uses as transport to and from the orbital stations.
• Space stations are man-made orbital structures that are designed for people to live on in outer space. A space station is distinguished from other manned spacecraft by its lack of major propulsion or landing facilities. Space stations are designed for medium-term living in orbit, for periods of weeks, months, or even years.

Fundamentals of Telecommunication

Telecomm:

The word telecommunication has taken from the French word telecommunication, meaning "far off", and the Latin communicare, meaning "to share". Telecommunication is that part of science that uses to transmit information by electromagnetic medium. And communication is a process of sharing of thoughts not by technological means. Telecommunication, however, is communication through technology meaning phones, Internet, radio etc... In today’s world, telecommunications involves the use of electrical components and devices such as the telegraph, telephone, as well as the use of radio and microwave communications system, optical fiber and their associated electronics, the use of the orbiting satellites and the Internet.

Revolution in wireless telecommunications started in the 1900s with pioneering developments in wireless radio communications by Nikola Tesla and Marconi. Other names that are associated with this revolution are:  Samuel Morse (telegraph), Alexander Graham Bell (telephone), Edwin Armstrong and Lee de Forest (radio), John Baird and Philo Farnsworth (television).

Basic elements

A basic telecommunication system consists of some primary units that are always present in some form:

• A transmitter that takes information and converts it into a signal.
• A transmission medium (physical channel) that carries the signal.
• A receiver that catches the signal from channel and converts it back into usable information.

Telecommunication over telephone lines is termed as point-to-point communication because it is between one transmitter to one receiver. Telecommunication through radio broadcasts is said as broadcast communication because it is between one powerful transmitter to the numerous low-power and sensitive radio receivers.

Telecom Networks:

A telecommunications network is a combination of links, terminals and nodes which connect to activate telecommunication among users of the terminal. Each terminal in the network must have a sole address so connections can be routed to the correct recipients. The collection of addresses in the network is called the address space. Some of them are:

• The aeronautical ACARS network
• Computer Networks
• The Internet
• The telephone network
• The global Telex network

The data network is used throughout the globe to connect particulars and organizations. Data networks can be connected to allow user’s seamless access to assets that are hosted outside of the picky provider they are connected to. The Internet is the best instance of many data networks from different organizations all in service under a single address space.
Terminals attached to TCP/IP networks are addressed using IP addresses. There are special types of IP addresses, but the most common is IP Version 4. Each unique address consists of 4 integers between 0 and 255, usually separated by dots when written down, e.g. 110.132.37.65.
TCP/IP is the fundamental protocols that provide the control and routing of messages across the data network. There are many different network structures that TCP/IP can be used across to professionally route messages, for example:

• Wide Area Networks (WAN)
• metropolitan area networks (MAN)
• local area networks (LAN)
• campus area networks (CAN)
• virtual private networks (VPN) .......................to be continued