Communication Systems and Different Research Topics

8/2/2019 Communication Systems and Different Research Topics

1/28

Presented by:

Ahmed Ahmedin

University of California, Davis

Communication Systems andDifferent Research Topics


2/28

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


3/28

Base band signal Features:

-Low frequency range is occupied. -no modulation is done.

-may be analog or digital.


4/28

Base band signal (cont.)Analog:

t


5/28

Base band signal (cont.)Analog:

BW

f

powerPower spectral density


6/28

Base band signal (cont.)Digital:


7/28

Base band signal (cont.)Digital:

1 1 11

0

1

0

1

00

Rb

Tb


8/28

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.


9/28

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.


10/28

3-Modulation techniques.

Analog (AM,FM)

Digital (ASK,FSK,PSK) (on square wave !!!)


11/28

2-Multiple access techniques

1-FDMA

2-TDMA

3-CDMA


12/28

FDMA

Strength

f1 f2 f3


13/28

B-multiple access techniques

1-FDMA


14/28

TDMA


15/28


2-TDMA


16/28

CDMA

Frequency

Strength


17/28


3-CDMA


18/28

CDMA


19/28

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


20/28

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


21/28

Nile University

Zweil University


22/28

Some Research Directions in NU

Cognitive Radio Network

Wireless Sensor Network (WSN)

Wireless Security


23/28

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.


24/28

Wireless Sensor Networks Secure sensor networks Location determination

Cross-layer optimization

Clustering algorithms


25/28

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.


26/28

My Work

Femtocells Interference Mitigation:


27/28


28/28

Thanks

Questions?

Communication Systems and Different Research Topics

Documents

Transcript of Communication Systems and Different Research Topics