Frequency-hopping spread spectrum

About: Frequency-hopping spread spectrum is a research topic. Over the lifetime, 5294 publications have been published within this topic receiving 60685 citations.

Anti-jamming broadcast communication using uncoordinated spread spectrum techniques

Abstract: Jamming-resistant communication is crucial for safety-critical applications such as emergency alert broadcasts or the dissemination of navigation signals in adversarial settings. In such applications, mission-critical messages are broadcast to a large and unknown number of (potentially untrusted) receivers that rely on the availability, integrity, and authenticity of the messages; here, availability primarily refers to the ability to communicate in the presence of jamming. Common techniques to counter jamming-based denial-of-service attacks such as Frequency Hopping (FH) and Direct Sequence Spread Spectrum (DSSS) cannot be applied in such settings because they depend on secret pairwise or group keys shared between the sender and the receivers before the communication. This dependency entails serious or unsolvable scalability and keysetup problems or weak jamming-resistance (a single malicious receiver can compromise the whole system). As a solution, in this work, we propose uncoordinated spread spectrum techniques that enable anti-jamming broadcast communication without shared secrets. Uncoordinated spread spectrum techniques can handle an unlimited amount of (malicious) receivers. We present two instances (Uncoordinated FH and Uncoordinated DSSS) and analyze differences in their performance as well as their combination. We further discuss the applications of these techniques to anti-jamming navigation broadcast, bootstrapping of coordinated spread spectrum communication, and anti-jamming emergency alerts.

Frequency-hopping spread-spectrum modulation for digital communications over electrical power lines

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. >

Hop-reservation multiple access (HRMA) for ad-hoc networks

Abstract: A new multichannel MAC protocol called hop-reservation multiple access (HRMA) for wireless ad-hoc networks (multi-hop packet radio networks) is introduced, specified and analyzed. HRMA is based on simple half-duplex, very slow frequency-hopping spread spectrum (FHSS) radios and takes advantage of the time synchronization necessary for frequency-hopping. HRMA allows a pair of communicating nodes to reserve a frequency hop using a reservation and handshake mechanism that guarantee collision-free data transmission in the presence of hidden terminals. We analyze the throughput achieved in HRMA for the case of a hypercube network topology assuming variable-length packets, and compare it against the multichannel slotted ALOHA protocol, which represents the current practice of MAC protocols in commercial ad-hoc networks based on spread spectrum radios, such as Metricom's Ricochet system. The numerical results show that HRMA can achieve much higher throughput than multichannel slotted ALOHA within the traffic-load ranges of interest, especially when the average packet length is large compared to the duration of a dwell time in the frequency hopping sequence, in which case the maximum throughput of HRMA is close to the maximum possible value.

Randomized Differential DSSS: Jamming-Resistant Wireless Broadcast Communication

Abstract: Jamming resistance is crucial for applications where reliable wireless communication is required. Spread spectrum techniques such as Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Spectrum (DSSS) have been used as countermeasures against jamming attacks. Traditional anti-jamming techniques require that senders and receivers share a secret key in order to communicate with each other. However, such a requirement prevents these techniques from being effective for anti-jamming broadcast communication, where a jammer may learn the shared key from a compromised or malicious receiver and disrupt the reception at normal receivers. In this paper, we propose a Randomized Differential DSSS (RD-DSSS) scheme to achieve anti-jamming broadcast communication without shared keys. RD-DSSS encodes each bit of data using the correlation of unpredictable spreading codes. Specifically, bit ``0'' is encoded using two different spreading codes, which have low correlation with each other, while bit ``1'' is encoded using two identical spreading codes, which have high correlation. To defeat reactive jamming attacks, RD-DSSS uses multiple spreading code sequences to spread each message and rearranges the spread output before transmitting it. Our theoretical analysis and simulation results show that RD-DSSS can effectively defeat jamming attacks for anti-jamming broadcast communication without shared keys.

Distributed code assignments for CDMA packet radio networks

Abstract: Code-division multi-access (CDMA) techniques allow many users to transmit simultaneously in the same band without substantial interference by using approximately orthogonal (low cross-correlation) spread-spectrum waveforms. Two-phase algorithms have been devised to assign and reassign spread-spectrum codes to transmitters, to receivers and to pairs of stations in a large dynamic packet radio network in polynomial times. The purpose of the code assignments is to spatially reuse spreading codes to reduce the possibility of packet collisions and to react dynamically to topological changes. These two-phase algorithms minimize the time complexity in the first phase and minimize the number of control packets needed to be exchanged in the second phase. Therefore, they can start the network operation in a short time, then switch to the second phase with the goal of adapting to topological changes. A pairwise code-assignment scheme is proposed to assign codes to edges. Simulations based on well-controlled topologies (sparse topologies) show that the scheme requires much fewer codes than transmitter-based code assignment, while maintaining similar throughput performance. >