Virtual Labs

Study of Modulation schemes with Memory, like MSK, GMSK etc.

1. In a coherent receiver for MSK, what is the primary challenge in demodulating the signal accurately?

a: Maintaining phase synchronization due to continuous phase modulation Explanation

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b: Separating overlapping amplitude levels at the detector Explanation

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c: Tracking the Gaussian filter response over multiple symbols Explanation

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d: Extracting the signal envelope under additive white Gaussian noise Explanation

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2. In GMSK, the memory introduced by Gaussian filtering primarily affects which aspect of the modulation?

a: The symbol's phase depends on multiple previous bits Explanation

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b: The carrier frequency is no longer stable Explanation

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c: Amplitude varies over time due to ISI Explanation

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d: Receiver requires non-coherent detection Explanation

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3. What is the key trade-off introduced when applying a narrow Gaussian filter in GMSK modulation?

a: Reduced ISI but increased group delay Explanation

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b: Improved power efficiency but reduced BER Explanation

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c: Better spectral compactness but increased ISI Explanation

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d: Lower noise figure but higher Doppler spread Explanation

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4. MSK can be viewed as a special case of which general modulation format?

a: Continuous Phase Frequency Shift Keying (CPFSK) Explanation

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b: Quadrature Amplitude Modulation (QAM) Explanation

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c: Differential Phase Shift Keying (DPSK) Explanation

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d: Orthogonal Frequency Division Multiplexing (OFDM) Explanation

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5. Which mathematical property ensures that MSK has a constant envelope signal?

a: The use of sinusoidal basis functions with orthogonal frequency shifts Explanation

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b: The matched filtering in the receiver stage Explanation

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c: The Gaussian pulse shaping filter at the transmitter Explanation

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d: The quadrature nature of I and Q components with synchronized transitions Explanation

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6. Why is GMSK preferred over MSK in systems like GSM even though it increases detection complexity?

a: It reduces adjacent channel interference significantly Explanation

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b: It uses variable amplitude for better control Explanation

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c: It allows higher data rates without ISI Explanation

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d: It simplifies synchronization and equalization Explanation

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7. In the context of bit error probability, why does MSK perform similarly to BPSK over AWGN channels?

a: Both use orthogonal signaling with coherent detection Explanation

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b: Both have minimum Euclidean distance between symbols Explanation

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c: MSK is equivalent to BPSK with phase continuity constraint Explanation

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d: MSK uses two amplitude levels just like BPSK Explanation

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8. Which condition must be satisfied for MSK signals to maintain orthogonality over the bit interval?

a: Frequency spacing = 1/(2 × bit duration) Explanation

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b: Symbol rate equals sampling rate Explanation

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c: Amplitude scaling factor equals √2 Explanation

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d: Gaussian filter bandwidth-time product equals 0.3 Explanation

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9. In practical implementation of GMSK, what makes the Viterbi algorithm suitable for demodulation?

a: GMSK introduces memory that can be modeled as a finite-state machine Explanation

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b: Viterbi decoding always improves BER in all modulation schemes Explanation

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c: The Viterbi algorithm simplifies Gaussian filtering Explanation

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d: It allows direct extraction of frequency deviation Explanation

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10. The eye diagram of GMSK typically appears closed compared to MSK because:

a: Gaussian filtering introduces ISI and phase memory Explanation

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b: The phase deviation exceeds π per symbol Explanation

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c: It uses amplitude modulation under Gaussian noise Explanation

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d: Higher sampling rates are used in GMSK Explanation

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