1. Hasan Hüseyin Çağlar
2. Cem Yusuf Aydoğdu
3. İrem Ertürk
4. Kutay Hekimoğlu
5. Berkay Köksal
6. Emin Mastizada

*Understanding What Modulation is

• -In General (Music, Medical …)
• -In  Network Technology

• Modulation is a process of mixing a signal with a sinusoid to produce a new signal. (Communication systems)

• The new signal, conceivably, will have certain benefits over an un-modulated signal.

• Sinusoid function f(t)=A.sin(w.t+θ)

*Basic Modulation Concepts

• Analog Modulation Techniques (AM, FM, PM,QAM)
• Digital Modulation Techniques (PSK, FSK,ASK,QAM)
• Others (Line Coding ,Pulse Modulation Methods)

• Describing superposition, linearity (non).

Using reasons and Benefits of Modulation

• Efficiency
• Overcome limitations
• Providing MA techniques
• Frquency usage
• …

Common modulation
techniques:

• ASK
• FSK
• PSK
• QAM

• Used in voice-band modems, DSL, coaxiacal cable modem applications

ASK

Binary representation of data with amplitudes

1. Advantages:

• Simple, cheap

2. Disadvantages:

• Susceptible to noise
• Less efficient

3. Application:

• Fiber optic cables

FSK

1. Advantages:

• Less susceptible to noise than ASK

2. Disadvantages:

• Higher cost than ASK
• Need more spectrum compared to ASK

3. Application:

• Over voice lines

Data bits are represented by frequency change

PSK

Phase of carrier signal is changed to represent data

1. Advantages:

• Less susceptible to noise
• Requires less bandwidth than FSK

2. Disadvantages:

• Higher cost than ASK
• More complex to detect signal

3. Application:

• Fiber-optic communication
• Coaxial communication

DSSS (Direct-Sequence Spread Spectrum )

What is the meaning of spread spectrum?

Transmitted signals covers the entire bandwith (frequency spectrum )

How DSSS spreads over entire bandwidth?

1. Chipping sequence(PN)

which has higher data rate and also longer bit sequences

2. Modulator (XOR)

Each bit in the original signal is represented by multiple bits after signal is transmitted into channel.

BPSK (Binary Phase-Shift Keying)

• Symbols are 1 bit long
• Uses two phases to represent  binary values
• These phases are  separated by 180°.

QPSK (Quadrature Phase Shift Keying)

• Symbols are two bit long and represent 4 binary value rather than 2(BPSK)
• Uses  four different phases.
• These phases are seperated by 90 degrees.

BPSK and QPSK

BPSK, 1 bit per symbol is encoded on the other hand QPSK has the capability to encode 2 bits per symbol. This feature doubles the data rates while staying within the same bandwidth.

OFDM (Orthogonal frequency-division multiplexing)

• OFDM is combination of modulation and multiplexing

• Orthogonality means one signal will not overlap with the other. (HOW?)

CELLULAR NETWORK STRUCTURE

Let’s go deeper!

Major air-interface access methods in cellular networks:

• Frequency Division Multiple Access (FDMA)
• Time Division Multiple Access(TDMA)
• Code Division Multiple Access(CDMA)

CELLULAR NETWORK EVOLUTION DIAGRAM

First Generation Cellular Network

• Critical Drawbacks
• Capacity is limited
• Poor handoff reliability
• No security and poor voice transmission

The most important aim is to increase the capacity! So, the solution…

• Only voice calls
• Analog signal is used

Second Generation Cellular Network

Some new Technologies has been developed such as GSM.
Addition to 1G specifications:

• TDMA
• GSM
• CDMA

These were the problem solvers at that time…

• Digital signals were used. So power consumption decreased.
• New services enabled such as sms, e mail
• Privacy protection increased

But later on, some additional necessities has come out.

2.5 Generation Cellular Network

GPRS

• Better use of radio and network resources.
• Completely transparent IP support

EDGE

• Has better modulation techniques that improves data-rate

TOWARDS 3G…

• Support both packet-switched and circuit switched data transmission
• Provides high data rate.
• Now, it can be used worldwide.

So, what has been changed?

2G vs 3G

4G

Radio-frequency identification (RFID) is the wireless use of electromagnetic fields to transfer data, for the purposes of automatically identifying and tracking tags attached to objects.

• Access management
• Tracking of goods
• Tracking of persons and animals
• Airport baggage tracking logistics
• Timing sporting events

Advantages of RFID usage

Scanning Range

 Tag does not necessarily need to
be within line of sight of the reader

RFID Capabilities

• RFID systems can scan multiple items simultaneous.
• RFID tags can contain more information
• RFID allow you to add or change data

Speed and Convenience

Cost Reduction

MUST PROVIDE POWER TO PASSIVE RF TAGS!

On-off keying (OOK)

Phase-shift keying(PSK)

Amplitude-shift keying(ASK)

Modulation Techniques that being used in RFID Readers

DSB-ASK

Simple but not that efficient

SSB-ASK

Requires an I/Q modulator

++++

• low bandwidth requirement
• power saving
• less effected by noise

----

• Complex modulation and demodulation circuitry
• Expansive in comparison to DSB

DE-Modulation Techniques that being used in RFID Readers

RFID Communication Protocols

EPCglobal Generation 1 Class 0
EPCglobal Generation 1 Class 1

1. Reader talk first
2. Tags can be read,written and killed in the process
3. Uses a Slotted-Aloha algorithm to avoid collisions

References

• (Modern Wireless Communications- Simon Haykýn, Michael Moher)
• http://global.britannica.com/EBchecked/topic/387402/modulation encyclopedia britanica
• http://telecommstuff.blogspot.com.tr/2011/01/benefits-of-modulation-in.html  Rayan Wijendra Almeida
• http://www.magnadesignnet.com/en/booth/technote/ofdm/page2.php
• http://www.cwins.wpi.edu/publications/pown/

References

• http://www.eecs.yorku.ca/course_archive/2010-11/F/3213/CSE3213_07_ShiftKeying_F2010.pdf
• http://www.radio-electronics.com/info/rf-technology-design/quadrature-amplitude-modulation-qam/8qam-16qam-32qam-64qam-128qam-256qam.php
• http://searchnetworking.techtarget.com/definition/QAM
• http://electronicdesign.com/communications/understanding-modern-digital-modulation-techniques#2
• http://www.slideshare.net/abdurrehmanabdurrehman391/chap-05-dsn?next_slideshow=1