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Communication Systems and Different Research Topics

This presentation by Ahmed Ahmed from the University of California, Davis, explores key aspects of wireless communication systems, including modulation techniques, transmission methods, and the challenges posed by noise and interference. It discusses baseband signal properties, analog versus digital transmission, and multiple access techniques like FDMA, TDMA, and CDMA. Additionally, it outlines different generations of mobile communication systems, cognitive radio networks, wireless sensor networks, and security measures. The presentation concludes with ongoing research areas and applications in the field, particularly femtocell interference mitigation.

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Communication Systems and Different Research Topics

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  1. Communication Systems and Different Research Topics Presented by: Ahmed Ahmedin University of California, Davis

  2. A-wireless communication aspects. 1-Modulation is the key 2-analog and digital transmission 3-bit rate 4-signal to noise ratio 5-jamming 6-interference 7-distortion 8-capacity

  3. Base band signal • Features: • -Low frequency range is occupied. • -no modulation is done. • -may be analog or digital.

  4. Base band signal (cont.) Analog: t

  5. Base band signal (cont.) Analog: Power spectral density power f BW

  6. Base band signal (cont.) Digital:

  7. Base band signal (cont.) Digital: 1 1 1 1 1 1 0 0 0 0 Tb Rb

  8. Transmission medium 1- Twisted-pair: It is very low bandwidth and it is easily tapped either physically or by monitoring its electromagnetic radiation 2- Coaxial cable: It is greater bandwidth than twisted-pair but it is very expensive. 3- optical fibers: It is very high bandwidth , very high bit rate and inherently transmission medium.

  9. Pass band transmission • Why wireless? 1- Long distance & less cost than wires. 2- mobility. • Why modulation? • Higher freq. lead to lower noise (no flicker !!!) • Antenna length proportional to wave length.

  10. 3-Modulation techniques. • Analog (AM,FM) • Digital (ASK,FSK,PSK) (on square wave !!!)

  11. 2-Multiple access techniques • 1-FDMA • 2-TDMA • 3-CDMA

  12. Strength f1 f2f3 FDMA

  13. B-multiple access techniques 1-FDMA

  14. TDMA

  15. B-multiple access techniques 2-TDMA

  16. Strength Frequency CDMA

  17. B-multiple access techniques 3-CDMA

  18. CDMA

  19. Noise Received info. Transmitted signal Received signal Info. Source User Transmitter Receiver Channel SOURCE Source Source encoder Channel encoder Modulator Destination Source decoder Channel decoder Demodulator Introduction Communication system consists of :- Transmitter Receiver

  20. D-Wireless different systems and mobile generations. Radio AMPS (Advanced mobile phone sys. Or Cordless) [1G] analog GSM [2G] digital GPRS [2.5G] EDGE [2.75G] UMTS [3G] then 3.5 & 3.75G LTE or WiMAX [4G] Wi-Fi Bluetooth Ultra wide band (UWB) [low dist. But high rates] Zigbee [low rate and low power consumption specially in industry] …..etc

  21. Nile University Zweil University

  22. Some Research Directions in NU • Cognitive Radio Network • Wireless Sensor Network (WSN) • Wireless Security

  23. Cognitive Radio Networks Research problems include: • Efficient and robust spectrum sensing. • Cognitive transmitter-receiver synchronization. • Exploration-vs-exploitation tradeoff. • Collaboration and competition among cognitive users. • Interference management in cognitive networks. • Centralized and decentralized scheduling in cognitive networks.

  24. Wireless Sensor Networks • Secure sensor networks • Location determination • Cross-layer optimization • Clustering algorithms

  25. Wireless Security • Practical secrecy capacity-achieving codes. • Secure broadcasting and multicasting. • Secrecy without transmit-CSI (channel state information). • Secrecy of MIMO channels. Authentication. • Cooperation for secrecy.

  26. My Work Femtocells Interference Mitigation:

  27. Thanks Questions?

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