Communication Systems and Different Research Topics

8/2/2019 Communication Systems and Different Research Topics

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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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2-TDMA


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CDMA

Frequency

Strength


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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?

Communication Systems and Different Research Topics

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