Sensitivity vs. Noise Figure: GSM, DECT, GPS & More

This article delves into the receiver sensitivity, input Signal-to-Noise Ratio (SNR), required Carrier-to-Noise Ratio (CNR), and noise figure for various wireless communication standards including GSM, EGSM, DCS1800, PCS1900, DECT, and GPS.

Receiver sensitivity is essentially the minimum input power level that a receiver in a wireless device needs to function effectively without issues. It’s the signal strength at which the required SNR and CNR are maintained for reliable communication. We’ll also look at the corresponding input noise level requirements.

The noise figure is closely tied to the noise factor, which quantifies how much noise is added to the input signal as it’s being amplified by the receiver. A lower noise figure indicates better receiver performance. The relationship is defined as:

$\text{Noise Figure (dB)} = 10 \cdot \log\_{10}(\text{Noise Factor})$

Where the Noise Factor is the ratio of the input SNR to the output SNR:

$\text{Noise Factor} = \frac{\text{Input SNR}}{\text{Output SNR}}$

Here’s a breakdown of the key parameters for different standards:

Key takeaways from the table:

• Receiver Sensitivity: Notice the wide range, from -130 dBm for GPS (requiring extremely weak signal detection) to -83 dBm for DECT. Lower (more negative) values indicate the ability to detect weaker signals.
• Input Noise: This represents the background noise level at the receiver input.
• Input SNR: The signal-to-noise ratio needed at the input for proper demodulation. Higher SNR generally indicates better performance.
• CNR: The carrier-to-noise ratio, a similar metric focused on the carrier signal strength relative to noise.
• Noise Figure: Reflects the amount of noise added by the receiver itself. Lower values are desirable.

Important Note on GPS: The negative Input SNR for GPS indicates that the signal is actually below the noise floor. GPS relies on sophisticated signal processing techniques (like spread spectrum) to extract the signal from the noise.