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ALLAH

ALLAH. Wireless & Mobile Communications. Compiled by : Engr.Muhammad Waseem Assistant Professor , Telecom Eng.Deptt . Sir Syed University of Engineering & Technology, Karachi, Pakistan. Email ID:engrmwaseem@gmail.com Office: CF-02,FFT-10. Channelization.

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ALLAH

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  1. ALLAH

  2. Wireless & Mobile Communications • Compiled by :Engr.MuhammadWaseem • Assistant Professor , Telecom Eng.Deptt. • Sir Syed University of Engineering & Technology, Karachi, Pakistan. • Email ID:engrmwaseem@gmail.com • Office: CF-02,FFT-10

  3. Channelization • Channelization is a multiple access method in which the available bandwidth of a link is shared in time, frequency ,or through code, between different stations. • The Channelization Protocols are FDMA, TDMA and CDMA

  4. Channelization( Conti…) • To accommodate a number of users, many traffic channels need to be made available. • In principle, there are three basic ways to have many channels within an allocated bandwidth: • Frequency Division Multiple Access (FDMA) • Time Division Multiple Access (TDMA) • Code Division Multiple Access (CDMA)

  5. Channelization ( Conti…) • In one BS radio service range, may be many MSs are located. • MS must distinguish which signal meant for itself among many signals being transmitted by other users. • BS should be able to recognize the signal sent by a particular user. • In cellular system, MS not only can distinguish a signal from a serving BS but also can discriminate the signal from adjacent BS. – Multiple access techniques important in mobile cellular system!

  6. Channelization( Conti…) • System employs different carrier frequency – FDMA system. • System uses distinct time – TDMA system. • System uses different code – CDMA system. • In wireless communications, it is necessary to utilize limited frequency bands at the same time, allowing multiple users(MSs) to share radio channel simultaneously. • To provide simultaneous two-way communication (duplex communication) : Frequency division duplexing (FDD) &Time Division Duplexing (TDD)

  7. Channelization( Conti…)

  8. FDMA (Frequency Division Multiple Access ) • In FDMA, the bandwidth is divided into channels. • The available bandwidth is shared by all stations. • Each Station uses its allocated band to send its data. • Each band is reserved for a specific station.

  9. FDMA(Cont…) • The band belongs to the station all the time .FDMA is a data link layer Protocol that uses FDM at the physical layer.FDMA is used in Cellular Telephone and Satellite Networks.

  10. FDMA(Cont…)

  11. FDMA(Cont…) • No synchronization and framing bits are needed. • Transmission is continuous in FDMA. • AMPS (first Analog Cellular System in the US) uses FDMA/FDD. • No restriction regarding the type of baseband or type of modulation • Capacity increase can be obtained by reducing the information bit rate and using efficient digital code.

  12. FDMA(Cont…) • No need for network timing. • Fairly efficient when the number of stations is small and the traffic is uniformly constant. • 48.6kbps bit rate. • ISI (Intersymbol Interference) is low.

  13. TDMA (Time Division Multiple Access)

  14. TDMA( Conti……)

  15. TDMA( Conti……) • In Time Division Multiple Access (TDMA) , the entire bandwidth is just one channel.The base stations share the capacity of the channel in time.Each station is allocated a time slot during which it can send data.TDMA is a data link layer Protocol that uses TDM at the Physical layer.

  16. TDMA( Conti……) • TDMA is used in the Cellular Telephone. • In TDMA, the bandwidth is just one channel that is timeshared. • Easy Handoff because of Idle Times. • Each Frame and slot starts with preamble containing synchronization information.

  17. TDMA( Conti……) • Non-Continuous Transmission is achieved. • Guard Time is required. • Data Transmission in bursts results in low battery consumption. • No need for precise narrowband filters • Easy for mobile or base stations to initiate and execute hands off

  18. TDMA( Conti……) • TDMA installations offer savings in base station equipment, space and maintenance • The most cost-effective technology for upgrading a current analog system to digital

  19. TDMA( Conti……)

  20. CDMA (Code Division Multiple Access)

  21. CDMA(Conti…..)

  22. CDMA(Conti…..) • In CDMA, one channel carries all transmission simultaneously. • CDMA is based on coding theory. • Each station(user) is assigned a code. • Everyone is speaking in different languages. • If voice volume is minimized, the number of people is maximized.

  23. CDMA(Conti…..) • The user’s signal is spread by a unique sequence. • All users share the same bandwidth with different sequences. • A communication is identified by the sequence. • Sender and receiver know the sequence in advance.

  24. CDMA (Conti…..) • Other ongoing communication appears to be noise. • CDMA is such a system ,which is based on Spread Spectrum Technology(a transmission technique in which data occupies a larger bandwidth than necessary(required) data.

  25. CDMA (Conti…..)

  26. THANKS TO ALLAH TALA

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