The Frequency Hopping Spread Spectrum (FHSS) is a data signal transmission method where data signals rapidly “hop” between frequencies to avoid interference and interception. The changes in frequency are determined by an algorithm only the transmitter and receiver know, making the pattern difficult to discern and the data signals resistant to eavesdropping.
The military uses FHSS in some of its radios. It is also used in consumer products, such as radio-controlled model drones and cars.
Read More about the Frequency Hopping Spread Spectrum
Learn more about FHSS below.
How Does Frequency Hopping Spread Spectrum Work?
Data signals travel from a transmitter to a receiver at a specific frequency. For example, your regular FM radio station would transmit signals at the same frequency every single time. A station at 101.9 FM means that the radio uses the 101.9 frequency to transmit its signal until the station decides to get a license for another frequency.
However, data signals are sent out in bursts at varying frequencies in the Frequency Hopping Spread Spectrum. The transmitter sends a small group of data at one frequency, then another group at another frequency, and so on, until all data signals are entirely transmitted.
The transmitter and receiver tune in to the next frequency whenever a chunk of data is transmitted. The choice of frequency is completely random and dependent on an algorithm that only the transmitter and receiver know. For this reason, both parties know which frequencies they are supposed to tune in.
Data transmission using FHSS happens quickly. In most cases, hopping occurs twice or more per second.
What Are the Advantages of the Frequency Hopping Spread Spectrum?
FHSS was primarily used by the military, but its usage has become more widespread over time because of its benefits. Below are some of the advantages of using the Frequency Hopping Spread Spectrum.
- Interference-resistant: Since signals rapidly hop from one frequency to another, there’s little chance of sharing the same frequency with other signals for an extended period. This multipath setup makes FHSS resistant to noise and interference, ensuring that data is transmitted completely.
- Safe: As long as only the transmitter and receiver know the hopping pattern or algorithm, nobody can intercept the data signals. Because of this security feature, several experts have advocated using FHSS in Internet of Things (IoT) networks.
- Multisupport: FHSS can share access points with many other data transmissions without causing significant interference.
- Jamming-resistant: Disrupting data transmission over the Frequency Hopping Spread Spectrum would be difficult without the hopping pattern. Therefore, as long as the pattern is unknown to other parties, the connection can’t be disrupted.
What Are the Disadvantages of the Frequency Hopping Spread Spectrum?
Like any other technology, there are downsides to using the Frequency Hopping Spread Spectrum, including:
- Slow data transmission: FHSS transmits data at a rate of 3Mbps. This speed is considered low compared to those of other transmission methods.
- Obsolete: The modulation method has become outdated. However, an adaptive FHSS (AFH) has been developed, an FHSS variation used in Bluetooth wireless technology.
- Prone to error: Frequency Hopping Spread Spectrum is only concerned with transmitting data signals safely with minimal interference. It has no mechanism checks for errors.
What Are the Differences between the Frequency Hopping Spread Spectrum and the Direct-Sequence Spread Spectrum (DSSS)?
FHSS and DSSS are often pitted against each other. To put things into perspective, Wi-Fi connections use DSSS.
FHSS involves sending chunks of data by hopping through different frequencies. On the contrary, DSSS doesn’t hop between frequencies. Like FHSS, data is divided into smaller groups, but they are sent at one spectrum of frequency simultaneously.
At the receiver’s end, an algorithm analyzes the chunks of data and converts them back into the original data.
While FHSS and DSSS use the same spread spectrum modulation method, they work differently. Below are some of the key differences between the two.
| Category | FHSS | DSSS |
| How they work | Data signals hop between different frequencies | Frequency stays the same |
| Signal transmission rate | Up to 3Mbps | Up to 11Mbps |
| Decoding | Straightforward | Requires an algorithm |
| Noise tolerance | Highly resistant to noise and interference | Sensitive and easily affected by noise |
| Distance consideration | Transmission doesn’t depend on distance | Distance affects DSSS data transmission |
Key Takeaways
- The Frequency Hopping Spread Spectrum (FHSS) is a data transmission method, where chunks of data signals rapidly “hop” between frequencies.
- The hopping mechanism helps make FHSS resistant to interference, jamming, and interception.
- The hopping pattern is determined by an algorithm that only the transmitter and receiver know.
- Keeping the pattern a secret is vital for data transmission security in FHSS.
- FHSS is used in military radios and consumer electronic products.
- AFH is a more advanced variation of FHSS used in Bluetooth technology.
- FHSS is often compared with DSSS, another spread spectrum data transmission technique that sends chunks of data at the entire frequency spectrum instead of hopping between different frequencies.
