Satellite Bandwidth Calculator : VSAT Bandwidth and Symbol Rate Formula
This calculator helps to 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 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
EXAMPLE of Satellite Bandwidth Calculator :
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 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.
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.
Useful converters and calculators
dBm to Watt converter
Stripline Impedance calculator
Microstrip line impedance
Antenna G/T
Noise temp. to NF