GPS Tutorials

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Some useful Website for Engineers

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How SMS Works in GSM


SMS Over Same Network






-In GSM Celluar network, an SMSC
 (SMS Center) is responsible for handling the SMS operations. 
-When a mobile generates a message, it first reaches the SMSC. SMSC then routes the message to its destination via Base Station/Tower.


-For SMS Control Channel r used.So a mobile can receive messages even if a voice or data call is going on.

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Global System for Mobile Communications

GSM (Global System for Mobile Communications) is a Digital Wireless Technology used for cell phone in the world that is, it is a cellular technology used for transmitting mobile voice and data services. It was developed by the European companies.

Features Of GSM
  • It is 2G Technology

  • GSM is a circuit-switched technology

  • Uses GMSK [Gaussian Minimum Shift Keying] Modulation

  • It supports FDMA & TDMA
  • It uses SIM card so u can easily switch your SIM card between phones
  • International roaming is easier on a GSM network
  • In GSM every user requires a separate frequency channel for communication
  • GSM accounts for 80% of total mobile phone technologies market

  • The Frequency Band(range) in GSM
    The frequency of the carrier is very important, because it determines the Size, power, efficiency of your mobile phones.


  • It supports FDMA & TDMA as Multiple Access Techniques







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Radio Frequency - RF Spectrum

Radio signals are transmitted through electromagnetic waves, also called radio waves, in radio communication system. The radio waves have a wide frequency range starting from a few ten kilo Hertz (kHz) to several thousand Mega Hertz (MHz). This wide range frequencies is called the radio spectrum or RF spectrum.

The RF spectrum is classified according to the applications of the spectrum in different service areas. The classification of the RF spectrum is given in below table along with the associated applications in communication system.

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Digital Microwave Communication


Microwave is a kind of electromagnetic wave. In a broad sense, the microwave frequency range is from 300 MHz to 300 GHz. But In microwave communication, the frequency range is generally from 3 GHz to 30 GHz.


Concept of Digital Microwave Communication

Digital microwave communication is a way of transmitting digital information in atmosphere through microwave or radio frequency (RF).


Microwave communication refers to the communication that use microwave as carrier.
Digital microwave communication refers to the microwave communication that adopts the digital modulation.

The baseband signal is modulated to intermediate frequency (IF) first . Then the intermediate frequency is converted into the microwave frequency.

The baseband signal can also be modulated directly to microwave frequency, but only phase shift keying (PSK) modulation method is applicable.

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Multiplexing Vs Multiple Access


Multiplexing

Multiplexing is the set of techniques that allows the simultaneous transmission of multiple signals across a single data link.

Multiple Access

If the physical links are shared by more than two nodes/users, it is said to be Multiple Access.


Categories of Multiplexing
a. Frequency Division Multiplexing (FDM)
b. Time Division Multiplexing (TDM)
c. Wave Division Multiplexing (WDM)

Categories of Multiple Access Methods
a.Frequency Division Multiple Access (FDMA) - flexible and simple
b.Time Division Multiple Access (TDMA) - popular
c.Code Division Multiple Access (CDMA Spread Spectrum) - highly secure

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