Virtual Labs

Study of effect of channel on system with various modulation

Which mathematical distribution best models the amplitude of a received signal in a Rayleigh fading environment without a line-of-sight (LoS) path?

a: Gaussian distribution b: Rayleigh distribution c: Rician distribution d: Poisson distribution

In a Rayleigh fading channel, which of the following strategies best mitigates deep fades without increasing transmit power?

a: Switching to high-order QAM. b: Implementing time diversity techniques. c: Reducing symbol rate. d: Using narrowband signals.

When AWGN is added to a Rayleigh fading channel, what combined impact does it have on BER performance?

a: It significantly improves BER performance. b: It results in a double-logarithmic BER increase. c: It causes a rapid BER degradation, especially at low SNR. d: It has negligible effect due to fading dominating.

How does the choice of modulation scheme affect the robustness of a signal in a Rayleigh fading channel with AWGN?

a: High-order modulation always improves robustness. b: Lower-order modulation is generally more robust against fading and noise. c: Modulation does not affect performance in fading channels. d: Only analog modulation is robust against fading.

In a wireless system experiencing Rayleigh fading and AWGN, which modulation scheme is generally more robust to deep fades without increasing transmit power?

a: High-order QAM (e.g., 64-QAM) b: Binary Phase Shift Keying (BPSK) c: 16-PSK d: Analog Amplitude Modulation (AM)

In digital communication systems, why is equalization essential when transmitting through a Rayleigh fading channel with AWGN?

a: It increases the transmitted signal power to overcome fading. b: It compensates for channel-induced distortions and intersymbol interference. c: It converts AWGN into a deterministic signal for easier demodulation. d: It changes the modulation scheme to avoid fading effects.

Under a Rayleigh fading model, how does the instantaneous SNR relate to the average SNR?

a: Always equal b: Always greater than average c: Always less than average d: Fluctuates around the average

How does the Doppler shift influence Rayleigh fading in mobile wireless scenarios?

a: It reduces the fading depth. b: It causes time-selective fading patterns. c: It increases SNR consistently. d: It converts Rayleigh fading to Rician fading.

Why does Rayleigh fading typically result in higher BER compared to AWGN-only channels at the same average SNR?

a: Because the channel bandwidth is lower. b: Because fading introduces deep nulls where signal amplitude can drop drastically. c: Because Rayleigh fading channels are always non-linear. d: Because phase distortion is completely absent.

In a digital communication system affected by Rayleigh fading and AWGN, which receiver technique primarily helps recover the transmitted signal accurately?

a: Increasing carrier frequency b: Using an adaptive equalizer c: Reducing the message signal amplitude d: Switching to analog transmission