Why Frequency Hopping Spread Spectrum (FHSS) Systems Are Critical For Machine Control

What Are Frequency Hopping Spread Spectrum (FHSS) Systems?

Frequency Hopping Spread Spectrum (FHSS) is a wireless communication method that offers several benefits, making it particularly important for operators using remote controls for their concrete line pumps. FHSS works by rapidly switching the carrier frequency among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. This approach enhances the reliability of wireless communications in environments prone to interference. 

Here's why FHSS is crucial for remote controls used in urban areas and on construction sites:

Improved Resistance to Interference

Construction sites are often filled with various electronic devices that can create a noisy radio frequency (RF) environment. As an example, devices such as walkie-talkies, other wireless remote controls, and machinery can cause interference that might disrupt the communication between your remote control and the machine you are operating. With FHSS, the system rapidly changes frequencies, making it less likely that interference on any single channel will disrupt the overall communication. 

Example of FHSS eliminating interference

Imagine a concrete line pump operator, concrete highrise pump, or a concrete placing boom is using a remote control with FHSS technology on a busy construction site. Nearby, several teams are using walkie-talkies on fixed frequencies, there are high-power cellular base stations and numerous wi-fi routers, and there's heavy machinery in operation, generating a broad spectrum of electromagnetic noise. 

Without FHSS, the remote control's signal might encounter interference from these devices, potentially causing loss of control over the pump, leading to over pouring, underpowering, or even a complete halt in operations.

With FHSS, the remote control and the pump's receiver are synchronized to hop frequencies together in a pattern unknown to other devices. If interference is encountered on one frequency, it only affects a fraction of a second of communication before the system hops to a new frequency, maintaining a stable and reliable connection. This ensures that the operator maintains control over the pump, directing it accurately despite the noisy environment, enhancing both safety and efficiency on the construction site.

Increasing Reliability by Decreasing Multipath Interference

By spreading the signal over multiple frequencies, FHSS systems are less susceptible to problems caused by multipath interference, where signals take multiple paths to reach the receiver, potentially causing phase cancellation or signal fading. This is crucial in urban or complex construction environments with lots of reflective surfaces. 

Multipath interference explained

Multipath interference occurs when signals transmitted from a wireless device reflect off surfaces like buildings, metal structures, or even the ground before reaching the receiver. These reflections cause the same signal to arrive at the receiver at slightly different times, creating multiple paths. When these multiple versions of the signal combine at the receiver, they can interfere with each other in two main ways:

Phase Cancellation: If two versions of the signal arrive in such a way that one's peak aligns with the other's trough (180 degrees out of phase), they can cancel each other out, leading to a significant drop in signal strength or even a complete loss of signal.

Signal Fading: Variations in signal strength can occur when the multiple paths constructively and destructively interfere with each other, causing the signal to fade in and out. This can lead to unreliable communication links, where the signal quality fluctuates dramatically, even with minor changes in the transmitter or receiver's position.

FHSS as a Solution to multipath interference

FHSS combats multipath interference by rapidly switching the carrier frequency of the transmitted signal in a pseudorandom sequence known to both the transmitter and receiver. This frequency hopping accomplishes two things:

Mitigating Phase Cancellation: By constantly changing frequencies, FHSS ensures that even if a signal at one frequency experiences phase cancellation due to multipath interference, the next frequency in the hopping sequence may not, thereby maintaining a more stable and reliable connection.

Reducing Signal Fading: As the system hops across a wide range of frequencies, the effects of signal fading are minimized. Certain frequencies might be more affected by reflections and refractions in a given environment, but as FHSS moves through its sequence, only a fraction of the hops are likely to experience severe fading at any given time.

Example of multipath interference in urban concrete line pump operation

Imagine a concrete highrise pump or a concrete placing boom operator working on a skyscraper foundation in a densely built-up urban area. The site is surrounded by tall buildings, cranes, and various metal structures, creating a challenging environment for wireless communication due to the high potential for signal reflections.

Without FHSS: A remote control operating on a fixed frequency could suffer from multipath interference. Signals could bounce off the surrounding buildings, leading to phase cancellation or fading right when precise control over the pump's flow is critical. This could result in erratic behavior of the pump, such as sudden stops or uncommanded bursts of concrete flow, potentially compromising safety and work quality.

With FHSS: The remote control for the concrete line pump uses FHSS technology. As the operator moves around the site and commands the pump, the control's signal is hopping through frequencies. Even if reflections cause interference at one frequency, the next hop is likely unaffected. This allows for smooth operation of the pump, accurate placement of concrete, and enhanced safety for the workers, even in the reflective and complex urban environment.

In summary, FHSS technology is crucial for remote machine control, particularly when operating in urban environments and range matters. FHSS mitigates multiple challenges, ensuring that operators of critical equipment can maintain control and efficiency, regardless of the complexity of their operating environment.

All of Aarcomm’s remote controls utilize Frequency Hopping Spread Spectrum (FHSS) systems to optimize the range, connectivity and reliability of our devices. Learn more about Aarcomm remote controls.