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Threat Mitigation
Published in Ron Burch, Resilient Space Systems Design: An Introduction, 2019
FHSS systems are more complicated than traditional single frequency systems because both the transmitter and the receiver must be precisely synchronized in time so as to hop according to a random code that defines the sequence of frequencies that each must use concurrently. Cryptographic devices are required to provide these secure codes. Spread spectrum waveforms can provide another type of robustness. By spreading their energy over a wide bandwidth, detection of the signal becomes more difficult as the peak signal power approaches the channel noise level. This class of waveform exhibits a low probability of detection (LPD) and a low probability of intercept (LPI). LPD waveforms are less susceptible to jamming, resulting in a measure of avoidance that also reduces the likelihood that it can be monitored.
Wireless networking
Published in Matthew N. O. Sadiku, Optical and Wireless Communications, 2018
Currently, frequency hopping spread spectrum (FHSS) offers a maximum data rate of 3 Mbps. It uses a narrowband carrier that changes frequency in a pattern known to both transmitter and receiver. It is based on the use of a signal at a given frequency that is constant for a small amount of time and then moves to a new frequency. The sequence of different channels for the hopping pattern is determined pseudorandomly — a very long sequence code is used before the sequence is repeated, over 65,000 hops, making it appear random. Thus, it is very difficult to predict the next frequency at which such a system will transmit/receive data as the system appears to be a noise source to an unauthorized listener, which makes FHSS very secure against interference and interception. FHSS is characterized by low cost, low power consumption, and less range than DSSS but greater range than infrared. Most WLAN systems use FHSS.
RFID Reader Synchronization
Published in Syed Ahson, Mohammad Ilyas, RFID Handbook, 2017
Kin Seong Leong, Mun Leng Ng, Alfio R. Grasso, Peter H. Cole
The U.S. FCC Title 47 Part 15.247, with operation within the band 902–928 MHz, uses the technique of frequency hopping spread spectrum (FHSS). FHSS is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. In the context of FCC Part 15.247 for a frequency hopping system operating in the 902–928 MHz band: if the 20 dB bandwidth of the hopping channel is <250 kHz, the system shall use at least 50 hopping frequencies and the average time of occupancy on any frequency shall not be >0.4 s within a 20 s period; if the 20 dB bandwidth of the hopping channel is 250 kHz or greater, the system shall use at least 25 hopping frequencies and the average time of occupancy on any frequency shall not be >0.4 s within a 10 s period. The maximum allowed 20 dB bandwidth of the hopping channel is 500 kHz. For an RFID system deployed in the United States following EPCglobal RFID protocol (EPCglobal, 2004), which is discussed in detail in the next part, a total of 50 channels are available, each with 500 kHz bandwidth. Hence the occupancy time on any channel cannot be >0.4 s within a 10 s period. In addition, a 1 W limit is allowed for systems employing at least 50 hopping channels with the use of antennas with directional gains that do not exceed 6 dBi, giving a maximum total radiated power of 4 W effective isotropic radiated power (EIRP). FHSS is adopted mainly in North and South America, though with a slight difference in the total bandwidth in different countries.
Renewable energy system paradigm change from trending technology: a review
Published in International Journal of Sustainable Energy, 2021
Vikas Khare, Cheshta Khare, Savita Nema, Prashant Baredar
Figure 5 shows the concept of internet of energy in the field of solar energy system. The overall system of electricity generation through solar energy system is proposed on the basis of power aware routing protocol. If the data of the overall solar system are collected through the mobile computing devices, then processes must be energy efficient. Power generated from the solar energy system also derived the radio frequency energy received from the signals in certain cases. Solar system sensor and actuators powered by radiation from nearby hotspot or access point can be used; power aware computing is required to run mobile devices efficiently. Solar data such as data of solar radiation, humidity and temperature data sent by the number of sensor devices can be clustered and aggregated at a server node of solar power plant. In internet of energy, the solar tracking system is operated by selective tuning and indexing technique. Selective tuning is a process by which a solar energy consumer selects pushed buckets or records of the tracking system, tunes to them and catches them. The term tuning means that a device is getting ready for caching at those instants and intervals of tracking of solar panel, when a selected record of interest is broadcasted. Power tracker high frequency converter of the solar system works on the concept of frequency hopping spread spectrum (FHSS). Spread spectrum frequencies can hop during each hopping interval, and hopping means moving by jumping forward and backward. FHSS is a method of transmitting user data using one of the carrier frequency channels in a given interval of time from multiple channels and then hop the channel frequency to another channel in the next interval of time. Consumer demand and domestic load are synchronised by the synchronisation software for mobile devices. A synchroniser is used for data synchronisation as per configuration, domain specific rules and conflict resolution strategies. HotSync or ActiveSync or IntelliSync synchronises the mobile devices when it connects to the generating end solar system server in the personal area network. As renewable energy is intermittent in nature, it needs battery along with controller, converters and inverters for power conditioning. Grid and specific RES are connected through the static switch to maintain continuity of supply. When the RES is not able to fulfil the load demand, switch connects the grid supply to the consumer load. Similar concept of IOT is also applicable in the field of wind, biomass and ocean energy system.