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Satellite Bandwidth Calculator: VSAT Bandwidth and Symbol Rate

bandwidth satellite communication symbol rate vsat calculator

This calculator helps determine the bandwidth required for a satellite communication link using the VSAT (Very Small Aperture Terminal) symbol rate and bandwidth formula. By inputting specific parameters such as data rate, modulation type, Forward Error Correction (FEC) rate, and roll-off factor, the calculator provides an estimate of the bandwidth needed for efficient data transmission.

Key Parameters

Key parameters used in the calculation of satellite bandwidth are as follows:

  1. Data Rate (kbps): The amount of data transmitted per second, measured in kilobits per second (kbps). It indicates the capacity of the link to handle data flow.
  2. Modulation Type: Specifies how data is encoded onto the carrier signal. Common types include QPSK, 8PSK, and 16QAM. Higher-order modulation schemes allow more data to be transmitted within the same bandwidth but may require a stronger signal.
  3. FEC Rate: The Forward Error Correction (FEC) rate indicates the proportion of error-correcting data added to the transmitted signal. For instance, an FEC rate of 3/4 means that 75% of the data is useful, while 25% is used for error correction.
  4. Roll-Off Factor: A parameter used in shaping the signal to minimize interference between adjacent channels. Typical roll-off factors range from 0.2 to 0.35, with a higher value increasing the required bandwidth.

Satellite Bandwidth Calculator

Inputs

Outputs

Note: This is for simplex link. For duplex, double the results obtained here.

INPUTS: Data rate = 1024 Kbps, Modulation Order = 2 (QPSK), FEC Rate = 0.75 (for 3/4), Roll off factor = 0.30

OUTPUTS: Symbol Rate = 682.67 KSPS, Occupied BW = 0.8874 MHz

VSAT Bandwidth and Symbol Rate Formula

The bandwidth required for a satellite link is calculated using the following formula:

  • Required Bandwidth (BW) = Symbol Rate × (1 + Roll-Off Factor)

The symbol rate is calculated based on the data rate, modulation type, and FEC rate:

  • Symbol Rate (SR) = Data Rate / (Modulation Efficiency × FEC Rate)

Modulation Efficiency: This value depends on the modulation type. For example:

  • QPSK: 2 bits per symbol
  • 8PSK: 3 bits per symbol
  • 16QAM: 4 bits per symbol

Once the symbol rate is determined, the bandwidth can be calculated by incorporating the roll-off factor. This ensures accurate estimation of the bandwidth required to transmit the desired data rate efficiently.

VSAT Bandwidth Formula

Example Calculation

Suppose a user wants to determine the bandwidth for a QPSK modulation with a data rate of 2000 kbps, FEC rate of 3/4, and roll-off factor of 0.25:

  • Symbol Rate (SR) = 2000 kbps / (2 × 3/4) = 2000 / 1.5 = 1333.33 kbaud

  • Required Bandwidth (BW) = 1333.33 kbaud × (1 + 0.25) = 1333.33 × 1.25 = 1666.67 kHz

  • This example shows that with these parameters, a bandwidth of 1666.67 kHz (or 1.67 MHz) is required for satellite communication.

Conclusion

The Satellite Bandwidth Calculator is a valuable tool for network planners and engineers to accurately estimate bandwidth requirements for satellite communication using VSAT systems. By inputting the desired data rate, modulation type, FEC rate, and roll-off factor, users can optimize their link budget and ensure efficient utilization of satellite resources.