Topic
Frequency agility
About: Frequency agility is a research topic. Over the lifetime, 646 publications have been published within this topic receiving 7040 citations.
Papers published on a yearly basis
1 / 2
Papers
1 Jan 1987
TL;DR: This paper outlines those features that distinguish the High Frequency (HF) Intra Task Force (ITF) Network from other packet radio networks, and presents a design concept for this network that encompasses organizational structure, waveform design, and channel access.
Abstract: The design of a packet radio network must reflect the operational requirements and environmental constraints to which it is subject. In this paper, we outline those features that distinguish the High Frequency (HF) Intra Task Force (ITF) Network from other packet radio networks, and we present a design concept for this network that encompasses organizational structure, waveform design, and channel access. Network survivability is achieved through the use of distributed network control and frequency hopping spread-spectrum signaling. We demonstrate how the execution of the fully distributed Linked Cluster Algorithm can enable a network to reconfigure itself when it is affected by connectivity changes such as those resulting from jamming. Additional resistance against jamming is provided by frequency hopping, which leads naturally to the use of code division mutiple access (CDMA) techniques that permit the simultaneous successful transmission by several users. Distributed algorithms that exploit CDMA properties have been developed to schedule contention-free transmissions for much of the channel access in this network. Contention-based channel access protocols can also be implemented in conjunction with the Linked Cluster network structure. The design concept presented in this paper provides a high degree of survivability and flexibility, to accommodate changing environmental conditions and user demands.
986 citations
TL;DR: The characteristics of spread spectrum systems have been examined in this paper, where the two primary techniques commonly used frequency hopping and direct sequence, are described along with their advantages and disadvantages, as well as their disadvantages.
Abstract: The characteristics of spread-spectrum systems that account for their growing use are examined. They offer low probability of intercept, signal hiding, and jammer rejection. Spread spectrum also provides a measure of immunity to multipath interference and multiple access capability, making it ideal for radar, telephone, local area networks, and many other applications. The two primary techniques commonly used frequency hopping and direct sequence, are described along with their advantages and disadvantages. >
274 citations
TL;DR: A novel signal processing approach is developed for coherent MIMO radar that effectively minimizes the arbitrary interferences generated by wireless systems from any direction, while operating at the same frequency using cognitive radio technology.
Abstract: The theoretical feasibility is explored of spectrum-sharing between radar and wireless communications systems via an interference mitigation processing approach. The new approach allows radar and wireless systems to operate at the same carrier frequency if the radar possesses a multiple-input multiple-output (MIMO) structure. A novel signal processing approach is developed for coherent MIMO radar that effectively minimizes the arbitrary interferences generated by wireless systems from any direction, while operating at the same frequency using cognitive radio technology. Various theoretical aspects of the new approach are investigated, and its effectiveness is further validated through simulation.
267 citations
TL;DR: This communication presents a new antenna system designed for cognitive radio applications that has been simulated with the driving motor being taken into consideration and a good agreement is found between the simulated and the measured antenna radiation properties.
Abstract: This communication presents a new antenna system designed for cognitive radio applications. The antenna structure consists of a UWB antenna and a frequency reconfigurable antenna system. The UWB antenna scans the channel to discover “white space” frequency bands while tuning the reconfigurable section to communicate within these bands. The frequency agility is achieved via a rotational motion of the antenna patch. The rotation is controlled by a stepper motor mounted on the back of the antenna structure. The motor's rotational motion is controlled by LABVIEW on a computer connected to the motor through its parallel port. The computer's parallel port is connected to a NPN Darlington array that is used to drive the stepper motor. The antenna has been simulated with the driving motor being taken into consideration. A good agreement is found between the simulated and the measured antenna radiation properties.
233 citations
TL;DR: A solution for the precise and cost-effective generation of frequency-hopping spread-spectrum waveforms using digital frequency synthesis based on read-only-memories (ROM, PROM, EPROM) is studied and computer simulations based on channel analysis to predict bit error probability are proposed and compared with measured results.
Abstract: A solution for the precise and cost-effective generation of frequency-hopping spread-spectrum waveforms using digital frequency synthesis based on read-only-memories (ROM, PROM, EPROM) is studied. For matched filter reception of frequency-hopping spread-spectrum waveforms a new approach based on lock-in amplifiers combined with synchronous voltage controlled oscillators (SVCO) brought remarkable results in practical field tests. An application-specific digital signal processor for receiver operation in form of a CMOS gate array was also designed. Prototypes according to two different system concepts were built, and measurements of bit error probability were carried out on indoor and outdoor power-line networks. Computer simulations based on channel analysis to predict bit error probability are proposed and compared with measured results. Indoor prototypes are designed for a data rate of 300 b/s and a frequency-hop rate of 900 s/sup -1/ with a transmission voltage approximately=0.35 V/sub rms/ in a spectral range from 30 to 146 kHz. Outdoor prototypes are intended for remote meter reading featuring a data rate of 60 b/s and a frequency-hop rate of 300 s/sup -1/. Transmission voltage is variable from 0.35 to 1 V/sub rms/ in a spectral range from 30 to 146 kHz. >
218 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2023 | 4 |
| 2022 | 3 |
| 2021 | 11 |
| 2020 | 12 |
| 2019 | 26 |
| 2018 | 24 |