PRESRNTER SUNNY BHOYAR

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PRESRNTER SUNNY BHOYAR

  1. 1. Prepared By Ibrahim AL-OBIDA 1/16
  2. 2. Prepared By Ibrahim AL-OBIDA 2/16 OutlineOutline Introduction Type of Multiplexing FDMA TDMA CDMA Future Work
  3. 3. Prepared By Ibrahim AL-OBIDA 3/16 IntroductionIntroduction The multiplexing is used to combined a number of independent signalsThe multiplexing is used to combined a number of independent signals into a composite signal suitable for transmission over a common channelinto a composite signal suitable for transmission over a common channel
  4. 4. Prepared By Ibrahim AL-OBIDA 4/16 Type of Multiplexing:Type of Multiplexing: 1. Frequency-Division Multiple Access (FDMA).1. Frequency-Division Multiple Access (FDMA). 3. Code-division Multiple-Access (CDMA)3. Code-division Multiple-Access (CDMA) 2. Time-Division Multiple Access (TDMA).2. Time-Division Multiple Access (TDMA).
  5. 5. Prepared By Ibrahim AL-OBIDA 5/16 Frequency-Division Multiple Access (FDMA)Frequency-Division Multiple Access (FDMA)  It is a communications technique that divides a communicationsIt is a communications technique that divides a communications channel into a number of equally spaced frequency bandschannel into a number of equally spaced frequency bands
  6. 6. Prepared By Ibrahim AL-OBIDA 6/16 Time-Division Multiple Access (TDMA)Time-Division Multiple Access (TDMA) It is a digital transmission technology that allows a number of users toIt is a digital transmission technology that allows a number of users to access a single radio-frequency (RF) channel without interference byaccess a single radio-frequency (RF) channel without interference by allocating unique time slots to each user within each channel.allocating unique time slots to each user within each channel.
  7. 7. Prepared By Ibrahim AL-OBIDA 7/16 Code Division Multiple Access (CDMA)Code Division Multiple Access (CDMA) is a wireless communications technology that uses theis a wireless communications technology that uses the principle of spread spectrum communication.principle of spread spectrum communication. There are three ways to spread the bandwidth of the signal:  Frequency hopping  Time hopping  Direct sequence
  8. 8. Prepared By Ibrahim AL-OBIDA 8/16 Code Division Multiple Access (CDMA)Code Division Multiple Access (CDMA) CDMA Features:CDMA Features: o All users use same frequency and may transmit simultaneouslyAll users use same frequency and may transmit simultaneously o Narrowband message signal multiplied by wideband spreadingNarrowband message signal multiplied by wideband spreading signal, or codewordsignal, or codeword o Each user has its own pseudo-codeword (orthogonal to others).Each user has its own pseudo-codeword (orthogonal to others). o Receivers detect only the desired codeword. All others appearReceivers detect only the desired codeword. All others appear as noise.as noise. o Receivers must know transmitter’s codeword.Receivers must know transmitter’s codeword.  CDMA is a Direct Sequence Spread Spectrum systemCDMA is a Direct Sequence Spread Spectrum system
  9. 9. Prepared By Ibrahim AL-OBIDA 9/16 Code Division Multiple Access (CDMA)Code Division Multiple Access (CDMA)
  10. 10. Prepared By Ibrahim AL-OBIDA 10/16 Code Division Multiple Access (CDMA)Code Division Multiple Access (CDMA) Pseudo-Noise Spreading
  11. 11. Prepared By Ibrahim AL-OBIDA 11/16 Code Division Multiple Access (CDMA)Code Division Multiple Access (CDMA) Direct Sequence Spread Spectrum System
  12. 12. Prepared By Ibrahim AL-OBIDA 12/16 Code Division Multiple Access (CDMA)Code Division Multiple Access (CDMA) Processing Gain: is the processing gain is Chipping Frequency (the bit rate of the PN code). is Information Frequency (the bit rate of the digital data). = fc fi
  13. 13. Prepared By Ibrahim AL-OBIDA 13/16 Code Division Multiple Access (CDMA)Code Division Multiple Access (CDMA) System Capacity: The capacity of a system is approximated by : is the maximum number of simultaneous calls is the processing gain is the total signal to noise ratio per bit is the inter-cell interference factor.
  14. 14. Prepared By Ibrahim AL-OBIDA 14/16 Code Division Multiple Access (CDMA)Code Division Multiple Access (CDMA) Advantages:Advantages: oIncreased capacityIncreased capacity oImproved voice qualityImproved voice quality oEliminating the audible effects of multipath fadingEliminating the audible effects of multipath fading oEnhanced privacy and securityEnhanced privacy and security oReduced average transmitted powerReduced average transmitted power oReduced interference to other electronic devicesReduced interference to other electronic devices Disadvantages:Disadvantages: oWide bandwidth per user requiredWide bandwidth per user required oPrecision code synchronization neededPrecision code synchronization needed
  15. 15. Prepared By Ibrahim AL-OBIDA 15/16 Code Division Multiple Access (CDMA)Code Division Multiple Access (CDMA) The Future Planning For Next SemesterThe Future Planning For Next Semester  We will evaluate interference and capacity inWe will evaluate interference and capacity in CDMA system and analysize them usingCDMA system and analysize them using MatLab simulatorMatLab simulator  Study the capacity of CDMAStudy the capacity of CDMA  Study the interference rises from the increasing ofStudy the interference rises from the increasing of capacity and how to reduce its effect.capacity and how to reduce its effect.
  16. 16. Prepared By Ibrahim AL-OBIDA 16/16 Than you for attendance Any question?

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