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The “System” in UAS
Published in R. Kurt Barnhart, Douglas M. Marshall, Eric J. Shappee, Introduction to Unmanned Aircraft Systems, 2021
Joshua Brungardt, Kurt Carraway
ISM frequency bands are widely used. This makes them susceptible to frequency congestion and signal interference, which can cause the UAS to lose communication with the ground station. Rapid frequency hopping has emerged as a technology that minimizes this problem. Frequency hopping is a basic signal modulation technique that spreads the signal across the frequency spectrum. With this technology, the transmitter operates in synchronization with the receiver, so both are tuned to the same frequency at the same time. During frequency hopping, a short burst of data is transmitted on a narrow band, then the transmitter tunes to another frequency and transmits again, and the process repeats. The hopping pattern can be from several times per second to several thousand times per second. The FCC has allowed frequency hopping on the 2.45 GHz unlicensed band. It is this repeated switching of frequencies during radio transmission that minimizes the effectiveness of unauthorized interception or jamming.
Introduction to Spread Spectrum Systems
Published in Jerry D. Gibson, Mobile Communications Handbook, 2017
Frequency hopping was first invented during World War II by Hedy Lamarr in a patent titled “Secret Communication System” [8]. In a frequency hopping spread spectrum system, the actual signal transmitted has narrow bandwidth. However, the center frequency of the transmission signal is varied over a wide band. The rate at which the center frequency of the signal is varied determines whether the system is a slow-hopping or fast-hopping system. The variation of the frequency, commonly referred to as hopping pattern, is usually based on a pseudorandom sequence. The advantage of a frequency hopping system is that its performance is not significantly affected by a narrow band interference source, since only the packets that are transmitted when the systems hops at the frequencies of the interfering signal are affected. The FH system also enables multiple point-to-point links in a given location if the hopping sequences used by the various links are effectively different. Note that the difference in the effective hopping pattern used by the various nodes could result from the use of different phases of the same hopping sequence for the various links. A block diagram of a typical FH spread spectrum signal is shown in Figure 13.3.
The “System” in UAS
Published in Douglas M. Marshall, R. Kurt Barnhart, Eric Shappee, Michael Most, Introduction to Unmanned Aircraft Systems, 2016
Joshua Brungardt, Richard Kurt Barnhart
ISM frequency bands are widely used making them susceptible to frequency congestion, which can cause the UAS to lose communication with the ground station due to signal interference. Rapid frequency hopping has emerged as a technology that minimizes this problem. Frequency hopping is a basic signal modulation technique used to spread the signal across the frequency spectrum. It is this repeated switching of frequencies during radio transmission that minimizes the effectiveness of unauthorized interception or jamming. With this technology, the transmitter operates in synchronization with a receiver, which remains tuned to the same frequency as the transmitter. During frequency hopping a short burst of data is transmitted on a narrowband, then the transmitter tunes to another frequency and transmits again, a process that repeats. The hopping pattern can be from several times per second to several thousand times per second. The FCC has allowed frequency hopping on the 2.45 GHz unlicensed band.
Traffic-aware autonomous scheduling for 6TiSCH networks
Published in International Journal of Computers and Applications, 2022
Nilam Pradhan, Bharat S. Chaudhari
The TSCH mode uses a combination of time-division and frequency-division multiple access (TDMA/FDMA). The objective of the development of TSCH is to achieve reliability and determinism in the network. The TSCH slotframe structure consists of fixed-size cells, where each cell represents a time offset and channel offset, corresponding to transmission period and frequency, respectively. Slotframe time is sliced into the timeslots to transmit a packet and receive an acknowledgment. It repeats over time, allowing devices to implement their communication schedule employing a transmit (Tx) or receive (Rx) slot with neighbor devices or a sleep cycle. The use of frequency hopping reduces the narrowband interference and multipath fading effects [7]. It enables network applications to meet reliable deterministic QoS by reducing collisions and energy consumption.
Design and Implementation of an Enterprise Credit Risk Assessment Model Based on Improved Fuzzy Neural Network
Published in Applied Artificial Intelligence, 2023
The frequency hopping varies over time, and the resulting time-frequency variation graph is known as the frequency hopping pattern. In transmitting corporate financial credit data, frequency hopping pattern design is crucial. If the enemy captures the frequency-hopping way, waveform tracking will likely interfere with it. Different frequency hopping pattern algorithms are typically employed on various occasions to improve communication security.