S20. How does decreasing SNR affect the choice of signal encoding and reception? Flashcards
What is SNR?
Signal-to-Noise Ratio (SNR) is a critical factor in communication systems.
What does high and low SNR mean?
High SNR indicates a clear signal with little noise, while low SNR indicates a noisy signal, which makes it harder to distinguish the signal from the noise. With low SNR, the choice of signal encoding and reception methods becomes crucial for maintaining reliable communication.
What kind of encoding schemes can be used with high SNR?
When SNR is high, more complex encoding schemes, such as QAM (Quadrature Amplitude Modulation), can be used. These schemes transmit more bits per symbol, improving data rates–however, they are sensitive to noise and require a high SNR to function effectively.
What kind of encoding schemes can be used with low SNR?
As SNR decreases, simpler encoding schemes are preferable, such BPSK (Binary Phase Shift Keying) and QPSK (Quadrature Phase Shift Keying).
Why is BPSK more robust against noise than QAM?
It transmits only one bit per symbol. This makes it less efficient in terms of data rate but more reliable in noisy environments, since there is a large distance between symbols in the signal constellation.
How is QPSK different from BPSK?
QPSK transmits two bits per symbol, it can achieve twice the data rate as BPSK but is also less noise-tolerant, though more so than higher-order modulation schemes like QAM.
How does decreasing SNR affect reception?
Decreasing SNR affects reception by making it more challenging to accurately decode the transmitted signal.
How are errors introduced by noise detected and corrected?
Error correction techniques such as FEC (Forward Error Correction) and ARQ (Automatic Repeat reQuest) are commonly used to detect and correct errors introduced by noise.
How can balance between data rate and reliability be maintained?
Adaptive modulation and coding (AMC) schemes can dynamically adjust the modulation type and error-correcting codes based on the current SNR. This adaptability helps maintain an acceptable balance between data rate and reliability as SNR fluctuates.
