Basic understanding of Telecommunication

Gunjan Shah

Jul 22, 2010 |

Posted in Analysts

This blog will give basic idea of telecommunication and important terminology used in telecom domain
Telecommunication system have three units
A) A transmitter that takes information and converts it to a signal.
B) A transmission medium, also called the “physical channel” that carries the signal.
C) A receiver that takes the signal from the channel and converts it back into usable information.
Telecommunication over telephone lines is called
1) Point-to-point communication :Between one transmitter and one receiver.
2) Broadcast communication in between one powerful transmitter and numerous low-power but sensitive receivers.
Analog or digital communications:
Communications signals can be either by analog signals or digital signals. Analog signal varied continuously with respect to the information.
In a digital signal, the information is encoded binary language. During the propagation and reception, the information contained in analog signals will inevitably be degraded by noise. And we want the output of a transmitter is noise-free for all practical purposes.
Communications networks
A communications network is a collection of transmitters, receivers, and communications channels that send messages to one another. Routers transmit information to the correct users. An analog communications network use switches to connect to form a connection between the two users. Communication network or switches required repeaters to amplify or recreate the signal when it is being transmitted over long distances.
Communication between two users:
The caller is connected to the person he wants to talk to by switches at various telephone exchanges. The switches form an electrical connection between the two users and the setting of these switches is determined electronically when the caller dials the number. Once the connection is made, the caller’s voice is transformed to an electrical signal using a small microphone in the caller’s handset. This electrical signal is then sent through the analog network to the user at the other end where it is transformed back into sound by a small speaker in that person’s handset. The separate electrical connection works in reverse to convert sound to electrical.
What is PSTN (public switched telephone network)
The public switched telephone network (PSTN) it is world’s public circuit-switched telephone networks. It is a worldwide net of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables connected by switching centers, which allows any telephone in the world to communicate with any other. The PSTN is entirely digital in its core and includes mobile as well as fixed telephones.
What are NPA and NXX?
The term NPA.NXX refers to the first six digits of a phone number, or prefix, as derived from the North American Number Plan (NANP). The area code is the first three digits and also referred to as a Number Plan Area or NPA. NXX refers to the exchange, which is the three digits following the area code. Together, they form a number unique to a specific Central Office (CO).
What is Global System for Mobile Communications (GSM)?
GSM, which stands for Global System for Mobile communications and is most widely used cell phone technology. Cell phones use a cell phone service carrier’s GSM network by searching for cell phone towers in the nearby area.
Cell phone carriers T-Mobile and AT&T use GSM for their cell phone networks. Sprint, Virgin Mobile and Verizon Wireless use the competing CDMA standard.

For practical and everyday purposes, GSM offers users wider international roaming capabilities than other U.S. network technologies and can enable a cell phone to be a “world phone”.
GSM also has the advantage of using SIM (Subscriber Identity Module) cards. The SIM card, which acts as your digital identity, is tied to your cell phone service carrier’s network rather than to the handset itself. This allows for easy exchange from one phone to another without new cell phone service activation.
What is Code Division Multiple Access (CDMA)?
CDMA, or Code Division Multiple Access, is a competing cell phone service technology to GSM, which is the world’s most widely used cell phone standard.

CDMA uses a “spread-spectrum” technique whereby electromagnetic energy is spread to allow for a signal with a wider bandwidth. This allows multiple people on multiple cell phones to be “multiplexed” over the same channel to share a bandwidth of frequencies.