Frequency Hopping Spread Spectrum Communication Research Articles

The invention by Hedy Lamarr and George Antheil of frequency-hopping spread-spectrum secret communications

Already before WW1, the general principles of using frequency agility to avoid detection and jamming had been proposed and actually used on a small scale. However, the limitations of the radio transmitters and receivers of the day made it impractical to implement systems that rapidly changed frequencies on a larger scale.

Improved Singleton bound on frequency hopping sequences and optimal constructions

Frequency hopping (FH) sequences play an important role in FH spread spectrum communication systems. In this paper, a new theoretical bound on the FH sequences with respect to the size of the frequency slot set, the sequence length, the family size, and the maximum periodic Hamming correlation is established. The new bound is tighter than the Singleton bounds on the FH sequences derived by Ding et al. (IEEE Trans Inf Theory 55:3297–3304, 2009) and Yang et al. (IEEE Trans Inf Theory 57:7605–7613, 2011) (first by Sarwate in: Glisic and Leppanen (eds) Code division multiple access communications, Springer, Boston, 1995). In addition, the new bound employes the M $$\ddot{\text {o}}$$ bius function. Then, more optimal FH sequence sets are obtained from Reed–Solomon codes. By utilizing the properties of cyclic codes, a new class of optimal FH sequence sets is obtained whose parameters meet the new bound. Further, two new constructions of FH sequence sets are presented. More new FH sequence sets are obtained by choosing proper base sequence sets. Meanwhile, the FH sequence sets constructed are optimal with respect to the new bound.

Fast carrier recovery in FHSS systems with DDS based Costas loop

Owing to fast change of carrier frequency, the usageof coherent demodulation methods in Frequency-Hopping SpreadSpectrum (FHSS) communication systems is limited by thecoherent state acquisition performed by the local oscillator. Toget around this difficulty, it is needed to implement the circuitwithin the FHSS system that is able to rapidly generate acoherent carrier. The work presented in this paper proposes arealization of Costas loop based on a combination of DirectDigital Synthesis (DDS), (Temperature-Compensated) Voltage-Controlled Oscillator ((TC)VCXO), and Phase-Locked Loop(PLL), which in particular enables a short period (less than 100μs) required for a local oscillator to reach the coherent state. Theimplemented model is thoroughly described with measurementsresults also provided.

Signal Diversity Modification Method to Overcome Partial Band Interference in Frequency Hopping Spread Spectrum Communication System

In this paper, a cost effective solution is proposed toovercome the Partial Band Interference problem in FrequencyHopping Spread Spectrum (FHSS) communication system. Thenumber of Hops per symbol per bit parameter value is modifiedto develop the cost effective solution. The Bit Error Rate (BER)versus Signal to Noise Ratio (SNR) or Eb/N plot is taken toanalyse the FHSS communication system performance properlyin the presence of Partial Band Interference. The entire abovespoken FHSS communication system modelling, simulation andperformance analysis are implemented and analysed usingMATLAB.

New designs of frequency hopping sequences with low hit zone

Frequency hopping sequences have been found wide applications in various modern frequency hopping spread spectrum communications and radar systems. With potential applications to these areas such as ultra wide bandwidth time hopping code division multiple access radio systems, multi-user and sonar systems, the design of quasi-synchronous time/frequency hopping code division multiple access systems by employing low hit zone hopping sequences has attracted wide attentions. In this paper, we present three construction methods for the low Hamming correlation zone frequency hopping sequences. The parameters of these sets of frequency hopping sequences with low hit zone are new and flexible. The constructed sequences are almost optimal and optimal respectively with respect to the Peng---Fan---Lee bounds. The simplicity of this technique makes it attractive for practical use.

Optimal Frequency Hopping Sequences: Auto- and Cross-Correlation Properties

Frequency hopping (FH) sequences play a key role in frequency hopping spread spectrum communication systems. In order to evaluate the performance of FH sequences, Lempel and Greenberger (1974) and Peng and Fan (2004) derived lower bounds on their Hamming auto- and cross-correlations. In this paper, we construct families of FH sequences with Hamming correlations meeting those bounds by combinatorial and algebraic techniques. We first construct optimal families consisting of a single FH sequence with maximum Hamming correlation equal to 2 from a combinatorial approach. Then we investigate families consisting of multiple FH sequences. We provide a combinatorial characterization for such families, and present a recursive method to construct them by means of this characterization. We also describe two algebraic constructions for such families of FH sequences, generalizing those of Ding, Moisio, and Yuan (2007). As a consequence, many new optimal families of FH sequences are obtained.

Diversity Combining and SNR Estimation for Turbo-Coded Frequency-Hopped Spread-Spectrum in Partial-Band Interference and Fading Channels

We compare different combinations of the repetition diversity order L and code rate R for turbo-coded Frequency-Hopped Spread-Spectrum (FH/SS) communication systems in the presence of fading and partial-band Gaussian interference. For a fixed overall channel code rate R/L we show that using the lowest code rate and no repetition diversity always performs better than using a higher code rate and some repetition for both coherent and non-coherent schemes. We then propose a simple maximum-likelihood-based method for signal-to-noise-ratio (SNR) estimation in Non-Coherent Binary Frequency Shift Keying (NCBFSK) without training symbols. Except for impractically small hop sizes of 8 bits or less we obtain performance virtually equal to that of perfect SNR knowledge but with much less complexity than iterative schemes previously proposed. For the case of Coherent Binary Phase Shift Keying (CBPSK) we derive the Expectation Maximization (EM) estimate of the SNR without training symbols and iteratively feed the estimator with the extrinsic information from the turbo decoder. The performance for CBPSK is near that of perfect SNR knowledge for hop sizes of 64 bits or more. Unlike previously proposed methods for CBPSK the EM estimate of SNR does not require knowledge of the noise and interference variance, received bit energy, or the fading channel model.

Lower Bounds on the Hamming Auto- and Cross Correlations of Frequency-Hopping Sequences

Frequency hopping (FH) sequences have found wide applications in various modern FH spread-spectrum communications and radar systems. In FH spread-spectrum communications, the interference occurs when two distinct transmitters use the same frequency simultaneously. In order to evaluate the goodness of FH sequence design, the Hamming correlation function is used as an important measure. In this correspondence, by considering separately the maximum Hamming autocorrelation sidelobe H/sub a/, and the maximum Hamming cross correlation H/sub c/, several new lower bounds on the size p of the frequency slot set F, the sequence length L, the family size M, and correlation properties are established. The new periodic bounds include the known Lempel-Greenberger bounds as special case when M=2, and are tighter than the Seay bounds under certain conditions when M>2. Furthermore, the new bounds disclose more information on the relationship between the maximum autocorrelation sidelobe and the maximum cross correlation compared with the Lempel-Greenberger bounds and Seay bounds. Besides, the aperiodic FH bounds which have not yet been previously reported are also presented and discussed in this correspondence.

Turbo product codes for FH-SS with partial-band interference

Turbo product codes (TPC) are investigated for use in frequency-hopping spread-spectrum (FH-SS) communications in partial-band interference. Binary orthogonal FSK is employed with noncoherent envelope detection. The Fossorier-Lin (1995) algorithm of soft-decision decoding based on ordered statistics is employed for soft-in/soft-out decoder instead of Chase (1972) algorithm to reduce the required E/sub b//N/sub J/ for a given packet failure probability. Performance of TPC for FH-SS with and without memory is evaluated by simulation. A numerical method to calculate the upper bound on performance is also given. The results show that the low-complexity TPC has a similar performance to the high-complexity convolutional turbo codes (CTC) for FH-SS without memory. For FH-SS with memory, full interleaving is used for TPC to achieve a good performance at low duty factors of partial-band interference.

Adaptive Equalization and Reed-Solomon Coding in High-Data-Rate Frequency-Hop Spread-Spectrum Communications

There is an increasing need for mobile packet radio networks that support link data rates of hundreds of kilobits per second to several megabits per second. If a radio network employing slow-frequency-hop (SFH) spread-spectrum modulation operates at these high data rates, however, the channel is likely to exhibit frequency-selective fading within each frequency slot of the SFH system. The frequency selectivity manifests itself as intersymbol interference at the receiver, and adaptive equalization must be employed in the receiver for each dwell interval in order to compensate for the intersymbol interference. In this paper, we examine the performance of a SFH spread-spectrum system with Reed–Solomon coding in a channel that exhibits time-selective and frequency-selective fading within each frequency slot. The performance is evaluated for systems in which the receiver employs maximum-likelihood sequence estimation in an equalizer that is retrained on a hop-by-hop basis. The performance of a receiver that uses errors-only decoding of Reed–Solomon codewords is considered. The use of the parity-bit method for erasure insertion and errors-and-erasures decoding is also investigated. The performance of a receiver that employs erasures of individual symbols only is compared with the performance of a receiver that also employs threshold-based erasures of entire dwell intervals. The effect of the system bandwidth and the Doppler spread on the comparison is also examined.

An adaptive-transmission protocol for frequency-hop wireless communication networks

An energy-efficient adaptive-transmission protocol for mobile frequency-hop spread-spectrum wireless communication networks is described and evaluated. The purpose of the protocol is to permit each...

Feedback phase-shift compensation for adaptive interference cancellers

An algorithm typically used for adaptive co-site interference cancellers (for frequency-hopping spread-spectrum communications systems) is the least-mean-square error (LMS) algorithm. As adaptive cancellation moves into L-band and S-band, feedback system stability becomes a critical issue for co-site interference cancellers using the LMS algorithm. The authors present a technique for compensating the high-frequency feedback path phase shifts leading to instability with an additional complex weight multiplication at baseband. Simulation and experimental results confirm the effectiveness of the technique.

Partial-band jammer suppression in FFH spread-spectrum system using FFT

This paper presents the performance evaluation of partial-band jammer suppression using fast Fourier transform (FFT) as an alternative in a fast frequency-hopped spread-spectrum (FFH/SS) communication system. The FFH/SS system employs a clipper to restrict the effect of a partial-band jammer before diversity combining. No additional side information of the jammer is required, and the analytical expression for the bit error rate (BER) is derived. It is shown that the performance of the FFT-based clipper receiver is better than that of the square-law linear combining receiver and comparable to that of the square-law clipper receiver.

Packet combining in frequency-hop spread-spectrum communication systems

The performance of frequency-hop spread-spectrum (FHSS) communication systems using hybrid automatic-repeat-request (ARQ) can be improved by combining current and prior transmissions at the receiver. Two methods for combining packets in systems that employ interleaving and Reed-Solomon (RS) coding are presented and analyzed for the partial-band interference channel. These methods use majority logic combining at the codeword level to make retransmission decisions. Bounded distance errors-and-erasures decoding and erasure generation by means of Viterbi's ratio threshold test (RTT) are incorporated in the analysis. Results of the analysis show that, with comparable packet error probabilities, the packet-combining schemes provide significant gains in throughput when compared with systems that do not employ combining.

Spectral-estimation-based acquisition for frequency-hopping spread-spectrum communications in a nonfading or Rayleigh-fading channel

Acquisition of frequency-hopping spread-spectrum (FH/SS) signals based on autoregressive spectral estimation is addressed for nonfading and Rayleigh-fading channels. The hopped frequency is synthesized using a linear feedback shift register (LFSR). The most significant bit (MSB) of the frequency estimate is loaded into the LFSR. A new acquisition logic is devised for the acquisition scheme that employs the autoregressive spectral-estimation acquisition technique (ASEAT). To characterize the statistical distributions of the frequency estimation error, the truncated Gaussian and uniform distributions are considered. The probability of the MSB error and the mean acquisition time of the acquisition logic are derived. For the ASEAT with the acquisition logic, the acquisition scheme that uses multiple antennas is also addressed. Numerical results for the probability of the MSB error and the corresponding mean acquisition time are illustrated for the performance evaluation of both cases.

Exact performance analysis of linear block codes in frequency-hop spread spectrum communication systems

We present a framework for determining the exact decoder error and failure probabilities for linear block codes in a frequency-hop communication channel with an arbitrary number of conditional symbol error and erasure probabilities. Applications are demonstrated for type-I hybrid ARQ systems by deriving equations for the packet error probability and throughput. Because these quantities are too small to be obtained by simulation, the framework provides exact results which are unobtainable by previous work.

Error rate for optimal follower tone-jamming

The performance of a countermeasure technique in the presence of the optimal follower multitone jammer is evaluated for frequency-hopped spread spectrum (FHSS) communications. It is shown that, with a certain probability, the optimal jammer will have dual tones in a frequency channel.

A low-power baseband receiver IC for frequency-hopped spread spectrum communications

A baseband receiver IC which will be incorporated into a low-power frequency-hopped spread spectrum (FH/SS) transceiver for 902-928 MHz ISM band applications is presented. The chip performs noncoherent binary/quaternary frequency shift keying (FSK) demodulation, equal-gain diversity combining of dual antenna branches, and symbol and frequency synchronization. The chip also accommodates variable data rates from 2 to 160 kb/s, programmable hop rates, and tunable bandwidth Loop filters. The core area of the 1-/spl mu/m CMOS chip is 3.9 mm/spl times/3.9 mm with a power consumption of 4.5 mW at 10 MHz from a 3-V supply. A baseband transceiver system utilizing this receiver chip for the prototype handset to demonstrate a point-to-point communication link is also described. Two XILINX FPGA chips were used to implement the remainder of the baseband transceiver functions, including frequency control logic for FSK modulation, acquisition control, data framing, symbol interleaving and deinterleaving, and interface control for data and voice.

Performance analysis of FHSS BFSK systems with nonlinear detectors in selective fading impulsive noise environment

In this paper, the noncoherent reception performance of frequency hopping spread spectrum communication systems operated in channels with impulsive noise and selective multipath fading characteristics is investigated. For the impulsive noise, the ε-contaminated mixture model is used. Binary frequency shift keying modulation and noncoherent demodulation are assumed and limiter-squarer detectors or squarers are used to detect signals. The bit error rates are obtained as functions of channel and system parameters, under the multihopping and multiuser synchronous multiple access case.

On a follower tone-jammer countermeasure technique

A countermeasure technique to a follower tone-jammer is evaluated for frequency-hopped spread spectrum communications. This technique utilizes randomized decisions by the transmitter and the receiver to lure the jammer into helping the communicator's performance part of the time. It is shown that the proposed technique reduces the bit error rate of the system.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>