QAM implementation using QAM implementation using LabVIEWLabVIEW

Talk FlowTalk Flow

What is QAM?What is QAM? Noise and Bit errorsNoise and Bit errors Pulse shaping FilterPulse shaping Filter ComparisonComparison Virtual Instrumentation and LabVIEWVirtual Instrumentation and LabVIEW Loops and StructuresLoops and Structures Front panel and Block Diagram for 16 QAMFront panel and Block Diagram for 16 QAM Constellation Diagram and eye diagramConstellation Diagram and eye diagram ResultResult AdvantagesAdvantages DisadvantagesDisadvantages ApplicationApplication ConclusionConclusion

What is QAM?

Quadrature amplitude modulation (QAM) is both an analog and a Quadrature amplitude modulation (QAM) is both an analog and a digital modulation scheme. digital modulation scheme.

QAM is a communication scheme that uses two carriers at the same QAM is a communication scheme that uses two carriers at the same frequency, but 90 degrees out of phase,i.e., in quadrature, to frequency, but 90 degrees out of phase,i.e., in quadrature, to modulate two separate message signalsmodulate two separate message signals

S(t) = m1 (t) cos (wct) + m2 (t) sin (wct) S(t) = m1 (t) cos (wct) + m2 (t) sin (wct)

The term M-QAM indicates that M voltage levels are used to encode The term M-QAM indicates that M voltage levels are used to encode n bits in each symbol, where M = 2^n. n bits in each symbol, where M = 2^n.

one of the popular methods known as 16-Quadrature Amplitude one of the popular methods known as 16-Quadrature Amplitude Modulation (16-QAM).Modulation (16-QAM).

QAM is an important modulation scheme because of its widespread QAM is an important modulation scheme because of its widespread adoption in current technologies. adoption in current technologies.

This scheme can be implemented in LabVIEW with the use of the This scheme can be implemented in LabVIEW with the use of the NI Modulation Toolkit. NI Modulation Toolkit.

Noise and Bit ErrorsNoise and Bit Errors

One important performance criterion in a digital communication One important performance criterion in a digital communication system is the bit error ratio (BER) .system is the bit error ratio (BER) .

It is the ratio of the number of incorrectly received bits to the total It is the ratio of the number of incorrectly received bits to the total number of transmitted bits. number of transmitted bits.

SNR is typically measured in terms of Eb=N0, where Eb is the SNR is typically measured in terms of Eb=N0, where Eb is the energy per bit and N0 is the noise power spectral density.energy per bit and N0 is the noise power spectral density.

Pulse shaping FilterPulse shaping Filter

Root raised cosine (RRC) filter.Root raised cosine (RRC) filter.

Parameters Parameters

Alpha Alpha

Filter lengthFilter length

ComparisonComparison

MODULATIONMODULATION BITS PER BITS PER SYMBOLSYMBOL

ERROR ERROR MARGINMARGIN

COMPLEXITYCOMPLEXITY

BPSKBPSK 11 1 11 1 Medium Medium

QPSKQPSK 22 1 / √2 0.71 1 / √2 0.71 Medium Medium

16 QAM16 QAM 44 √√2 / 6 0.23 2 / 6 0.23 High High

64 QAM64 QAM 66 √√2 / 14 0.1 2 / 14 0.1 High High

Virtual Instrumentation and LabVIEWVirtual Instrumentation and LabVIEW

Virtual Instrumentation is the use of customizable software and Virtual Instrumentation is the use of customizable software and modular measurement hardware to create user-defined modular measurement hardware to create user-defined

measurement systems, called virtual instruments.measurement systems, called virtual instruments.

Lab VIEW ties the creation of user interfaces (called front panels) Lab VIEW ties the creation of user interfaces (called front panels) into the development cycle. Lab VIEW programs/subroutines are into the development cycle. Lab VIEW programs/subroutines are called virtual instruments (VIs). Each VI has three components:called virtual instruments (VIs). Each VI has three components:

1. Block diagram1. Block diagram

2. Connector pane 2. Connector pane

3. Front panel3. Front panel

A key benefit of LabVIEW over other development environments is A key benefit of LabVIEW over other development environments is the extensive support for accessing instrumentation hardware.the extensive support for accessing instrumentation hardware.

Powerful, flexible, and scalable design. Powerful, flexible, and scalable design.

Easy to learn, use, maintain, and upgrade .Easy to learn, use, maintain, and upgrade .

Loops and StructuresLoops and Structures

Event structureEvent structure

Like a Case Structure, the Event Structure contains multiple Like a Case Structure, the Event Structure contains multiple subdiagrams, each of which is configured to handle one or more subdiagrams, each of which is configured to handle one or more eventsevents, which are user actions such as , which are user actions such as Key Down Key Down or or Mouse MoveMouse Move. .

While loopWhile loop

It repeats the subdiagram inside it until the conditional terminal, an It repeats the subdiagram inside it until the conditional terminal, an input terminal, receives a particular Boolean value. input terminal, receives a particular Boolean value.

Flat sequence structureFlat sequence structure

It consists of one or more sub diagrams, or frames, that execute It consists of one or more sub diagrams, or frames, that execute sequentially.sequentially.

FRONT PANEL FOR 16 QAMFRONT PANEL FOR 16 QAM

BLOCK DIAGRAMBLOCK DIAGRAM

Constellation Diagram and eye diagramConstellation Diagram and eye diagram

The constellation points are usually arranged in a square grid with The constellation points are usually arranged in a square grid with equal vertical and horizontal spacing.equal vertical and horizontal spacing.

is an oscilloscope display in which a digital data signal from a is an oscilloscope display in which a digital data signal from a receiver is repetitively sampled and applied to the vertical input, receiver is repetitively sampled and applied to the vertical input, while the data rate is used to trigger the horizontal sweep. while the data rate is used to trigger the horizontal sweep.

ResultResult

Given parameters: Given parameters: Samples per symbol = 16, Symbol rate = 1000Hz, Message bits = Samples per symbol = 16, Symbol rate = 1000Hz, Message bits =

500, Eb/N0 = 81.03 dB, Root raised cosine filter with alpha = 0.5 500, Eb/N0 = 81.03 dB, Root raised cosine filter with alpha = 0.5 and filter length = 8.and filter length = 8.

The constellation and eye diagram for given parameters is as shown The constellation and eye diagram for given parameters is as shown belowbelow

AdvantagesAdvantages

QAM is an attractive alternative to SSB-SC. QAM is an attractive alternative to SSB-SC.

QAM is more exacting in terms of the carrier frequency QAM is more exacting in terms of the carrier frequency and phase or the requirement for a distortion-less and phase or the requirement for a distortion-less transmission medium.transmission medium.

QAM appears to increase the efficiency of transmission QAM appears to increase the efficiency of transmission for radio communications systems by utilising both for radio communications systems by utilising both amplitude and phase variations. amplitude and phase variations.

DisadvantagesDisadvantages

it is more susceptible to noise. it is more susceptible to noise.

linearity must be maintained. linearity must be maintained.

APPLICATIONSAPPLICATIONS

Cable communication for the transmission of DTV.Cable communication for the transmission of DTV.

Internet traffic between cable modem and modem Internet traffic between cable modem and modem termination systems.termination systems.

In many radio communications and data delivery In many radio communications and data delivery applications. applications.

CONCLUSIONCONCLUSION

QAM is an important modulation scheme because of its QAM is an important modulation scheme because of its widespread adoption in current technologies. widespread adoption in current technologies.

Moreover, this scheme can be implemented in LabVIEW Moreover, this scheme can be implemented in LabVIEW with the use of the NI Modulation Toolkit. with the use of the NI Modulation Toolkit.

This toolkit, in conjunction with the vector signal This toolkit, in conjunction with the vector signal generator and vector signal analyzer, implements QAM generator and vector signal analyzer, implements QAM for signals in the real world.for signals in the real world.

THANK YOUTHANK YOU