Post on 05-Apr-2018
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Presented by:
Ahmed Ahmedin
University of California, Davis
Communication Systems andDifferent Research Topics
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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-distortion8-capacity
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Base band signal Features:
-Low frequency range is occupied. -no modulation is done.
-may be analog or digital.
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Base band signal (cont.)Analog:
t
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Base band signal (cont.)Analog:
BW
f
powerPower spectral density
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Base band signal (cont.)Digital:
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Base band signal (cont.)Digital:
1 1 11
0
1
0
1
00
Rb
Tb
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Transmission medium
1- Twisted-pair:
It is very low bandwidth and it is easily tapped eitherphysically or by monitoring its electromagnetic radiation
2- Coaxial cable:
It is greater bandwidth than twisted-pair but it is veryexpensive.
3- optical fibers:It is very high bandwidth , very high bit rate and inherently
transmission medium.
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Pass band transmission Why wireless?
1- Long distance & less cost than wires.2- mobility.
Why modulation?
1. Higher freq. lead to lower noise (no flicker !!!)
2. Antenna length proportional to wave length.
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3-Modulation techniques.
Analog (AM,FM)
Digital (ASK,FSK,PSK) (on square wave !!!)
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2-Multiple access techniques
1-FDMA
2-TDMA
3-CDMA
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FDMA
Strength
f1 f2 f3
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B-multiple access techniques
1-FDMA
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TDMA
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B-multiple access techniques
2-TDMA
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CDMA
Frequency
Strength
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B-multiple access techniques
3-CDMA
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CDMA
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Introduction
19
Communication system consists of :-
SourceSourceencoder
Channelencoder
Modulator
DestinationSourcedecoder
Channeldecoder
Demodulator
Transmitter
Receiver
SOURCE
Info.Transmitter
Transmitted
signal
Received
signalReceiver
Received
info.
Noise
ChannelSource User
ti
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generations.
1. Radio
2. AMPS (Advanced mobile phone sys. Or Cordless) [1G]
analog
3. GSM [2G] digital
4. GPRS [2.5G]
5. EDGE [2.75G]
6. UMTS [3G] then 3.5 & 3.75G
7. LTE or WiMAX [4G]
8. Wi-Fi
9. Bluetooth
10. Ultra wide band (UWB) [low dist. But high rates]
11. Zigbee [low rate and low power consumption specially inindustry]
12. ..etc
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Nile University
Zweil University
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Some Research Directions in NU
Cognitive Radio Network
Wireless Sensor Network (WSN)
Wireless Security
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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 incognitive networks.
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Wireless Sensor Networks Secure sensor networks Location determination
Cross-layer optimization
Clustering algorithms
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Wireless Security Practical secrecy capacity-achieving codes. Secure broadcasting and multicasting.
Secrecy without transmit-CSI (channel stateinformation).
Secrecy of MIMO channels. Authentication.
Cooperation for secrecy.
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My Work
Femtocells Interference Mitigation:
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Thanks
Questions?