labAlive - Virtual Communications Lab

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Introduction

Oscilloscope

Spectrum analyzer

Experiments

FFT illustrated

Spectrum analyzer

OFDM step-by-step

OFDM Guard interval

OFDM BER vs Eb/N0

Multipath fading

QPSK BER

QAM BER

Equivalent baseband

Wi-Fi IEEE 802.11ac

Doppler shift

Tutorials

Fourier transforms

FFT summary

FFT spectrum analyzer

OFDM step-by-step

OFDM PAPR

OFDM BER vs Eb/N0

QPSK BER

QAM BER

Simulation Apps

Wireless Communications

Telecommunications

Digital Modulation

All

Calculator

FFTIFFT

FFTIFFT power invariant

erfc(x) Q(x)

QAM bit error probability

dB

User Manual

Systems & measures

Measure settings

Menu

Keys

Developer

Quick Start

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Learn communications technology - check out these hands-on web-based experiments

Doppler shift

Doppler shift in wireless communications

In channels where the receiver moves the signal frequency is shifted depending on the velocity. The Doppler effect can be observed in wireless communications.
QAM constellation diagram

QAM BER for AWGN channel

Analyse the bit error rate of M-QAM over an AWGN channel. Adjust Eb/N0 and the constellation size. Compare the measured BER to the analytical bit error probability.
Transfer function of the extended pedestrian A model

Multipath fading propagation | Extended Pedestrian A model

Even small movements strongly impact the frequency-selective channel characteristics. Fast fading describes mobile radio channels.
QAM constellation diagram

OFDM transmission step-by-step

Understand OFDM and process each step using example values. A pilot sequence initializes the equalizer. Transmit an OFDM symbol and detect ISI-free.
Transfer function of the extended pedestrian A model

Guard interval | ISI-free OFDM transmission

The guard interval must be longer than the delay spread of the channel. Modify the echo-delay of a fading channel and check the constellation points for ISI.
FFT example discrete sinc

OFDM Peak-to-average ratio

When OFDM subcarriers add up coherently the power of the transmitted signal is N times the average power. Thus, the PAPR of an OFDM system is N.
QAM constellation diagram

Wi-Fi IEEE 802.11ac physical layer parameters

This simulation implements a Wi-Fi transmission (80 MHz, VHT-MCS 6, 400 ns guard interval). Analyze the signals, e.g. the transmit spectrum.
FFT example discrete sinc

Fast Fourier transform (FFT)

Example time signals and corresponding frequency signals illustrate the FFT: DC component, Dirac pulse, cosine, pulse, complex rotating phasor...
LTI system output signal - amplitude and phase change

Oscilloscope | Low-pass filter

Measure amplitude and phase of the output sine wave signal using an oscilloscope. Compare the results with the transfer function representing the linear time-invariant (LTI) system.
Audio signal

Audio signals

Measure audio signals in the time and frequency domain. Select music wav file, microphone or signal generator waveform as input. Listen to the signal.
Signal-to-noise ratio

Signal-to-noise ratio SNR

A visual and audio demonstration of signal qualities measured by the signal-to-noise ratio (SNR). Examples of signals and the impact of added noise are shown.
QPSK spectrum

Spectrum analyzer

Control the settings of an FFT spectrum analyzer. Sampling time and capture time determine the spectrum's highest available frequency and resolution bandwidth.
FM signal spectra

Spectra of FM signals

Frequency modulation signal spectra show sidebands for sinewave modulation. In this experiment we take a look how they change with the modulating signal amplitude.
Amplitude modulation

Amplitude modulation

By the invention of amplitude modulation radio broadcasting was made possible. Analyze an AM-signal in time and frequency domain by changing the parameters of the modulation.

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