Write short notes on the following (i) GSM (ii) CDMA (iii) WLL (iv) 3G (v) SMS (vi) EDGE (vii) UMTS

Q. Write short notes on the following:

(i) GSM

(ii) CDMA

(iii) WLL

(iv) 3G

(v) SMS

(vi) EDGE

(vii) UMTS

Answer =

(i) GSM:-

GSM (Global System for Mobile) communications is a technique that uses narrowband TDMA, which allows eight simultaneous calls on the same radio frequency. TDMA is short for Time Division Multiple Access. TDMA technology uses time-division multiplexing (TDM) and divides a radio frequency into time slots and then allocates these slots to multiple calls thereby supporting multiple, simultaneous data channels.

(ii) CDMA:-

CDMA (Code Division Multiple Access) uses a spread-spectrum technique where data is sent in small pieces over a number of discrete frequencies. Each user's signal is spread over the entire bandwidth by unique spreading code. At the receiver end, the same unique code is used to recover the signal.

Or

CDMA (Code-Division Multiple Access) on the other hand, unlike GSM, does not assign a specific frequency to each user. CDMA uses spread-spectrum technique where every channel uses full available spectrum. With CDMA, data is sent in small pieces over a number of discrete frequencies available for use at any time in the specified range. All users transmit in the same wide-band chunk of spectrum. Each user's signal is spread over the entire bandwidth by a unique spreading code, which is again used at the receiver end to recover the transmitted signal.

(iii) WLL:-

In WLL services, the telephone provided is expected to be as good as wired phone. Its voice quality must be high - a subscriber carrying out long conversation must not be irritated with quality: one must be able to use speakerphones, cordless phones and parallel phones. The telephone must support fax and modem communications and should be connectable to a Public Call Office.

WLL is a system that connects subscribers to the public switched telephone network (PSTN) using radio signals as a substitute for other connecting media.

Or

A WLL (Wireless in Local Loop) system serves a local area by deploying a multiplicity of multichannel transmit/receive base stations (transceivers) that are within line-of-site of the intended customers. Each customer is equipped with a mini-station of low power, into which the telephone (or PBX) is connected. When calls are made from the telephone, it signals the base station for a connection, which is subsequently established through a switch center, exactly as in conventional telephony. An incoming call is identified at the switch center and routed to the base station assigned to serve the telephone being called. The wireless connection is then made, and the call is completed in a conventional manner. The infrastructure design of a WLL system typically uses an advanced transmission technology such as CDMA, which permits support of large subscriber bases through orderly expansion of the base station clusters.

(iv) 3G:-

3G (Third Generation) mobile communications technology is a broad band, packet-based transmission of text, digitized voice, video, and multimedia at data rates up to and possibly higher than 2 megabits per second (Mbps), offering a consistent set of services to mobile computer and phone users no matter where they are located in the world.

(v) SMS:-

Short Message Service (SMS) is the transmission of short text messages to and from a mobile phone, fax machine and/or IP address.

(vi) EDGE:-

Edge computing optimizes Internet devices and web applications by bringing computing closer to the source of the data. This minimizes the need for long distance communications between client and server, which reduces latency and bandwidth usage.

(vii) UMTS:-

The Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. UMTS uses wideband code division multiple access (CDMA) radio access technology to offer greater spectral efficiency and bandwidth to mobile network operators.