Orthogonal Frequency Division Multiplexing

What is the main advantage of OFDM over single-carrier systems?

a: Requires less bandwidth Explanation

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b: Reduced transmitter complexity Explanation

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c: Converts frequency-selective fading into flat fading per subcarrier Explanation

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d: Eliminates the need for channel coding Explanation

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Which of the following systems uses OFDM?

a: AM radio Explanation

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b: GSM Explanation

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c: Wi-Fi (802.11a/g/n/ac/ax) Explanation

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d: CDMA Explanation

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What ensures orthogonality among subcarriers in OFDM?

a: Using different modulation schemes per subcarrier Explanation

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b: Time separation between subcarriers Explanation

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c: Subcarriers are spaced at multiples of the inverse of the OFDM symbol duration Explanation

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d: Equal power allocation Explanation

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The frequency spacing between subcarriers in OFDM is:

a: Arbitrary Explanation

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b: Equal to the channel bandwidth Explanation

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c: Equal to 1/(OFDM symbol duration) Explanation

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d: Dependent on the SNR Explanation

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Which of the following is used to mitigate Inter-Symbol Interference (ISI) in OFDM?

a: Raised cosine filter Explanation

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b: Cyclic prefix Explanation

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c: Low-pass filter Explanation

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d: Guard bands Explanation

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OFDM is particularly effective in which type of channel?

a: AWGN only Explanation

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b: Frequency-selective fading Explanation

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c: Flat fading Explanation

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d: Interference-limited channels Explanation

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What is the role of the Inverse Fast Fourier Transform (IFFT) in an OFDM transmitter?

a: Modulate data onto the carrier frequency Explanation

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b: Convert frequency-domain symbols into time-domain waveform Explanation

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c: Filter out noise Explanation

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d: Demodulate the signal Explanation

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In OFDM, the cyclic prefix should be:

a: Equal to the symbol duration Explanation

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b: Longer than the entire OFDM frame Explanation

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c: Longer than the channel delay spread Explanation

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d: Equal to the number of subcarriers Explanation

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What type of equalizer is commonly used in OFDM systems?

a: Time-domain FIR filter Explanation

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b: Frequency-domain scalar equalizer Explanation

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c: LMS adaptive equalizer Explanation

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d: Decision feedback equalizer Explanation

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