Partial-band Noise Jamming Research Articles

Performance study of fast frequency-hopped/ M -ary frequency-shift keying systems with timing and frequency offsets over Rician-fading channels with both multitone jamming and partial-band noise jamming

In this study, the effects of timing and frequency offsets on bit-error rate (BER) performance of fast frequency-hopped M-ary frequency-shift keying communication systems over Rician-fading channels with both multitone jamming (MTJ) and partial-band noise jamming (PBNJ) are investigated. Analytical BER expressions are derived for both linear-combining and product-combining receivers. Numerical results show that under both MTJ and PBNJ conditions, the BER performance falls between the two extreme cases, in which either MTJ or PBNJ presents. It is found that the BER performance is severely degraded as the timing or frequency offset increases. The product-combining receiver is found to be more sensitive to the timing and frequency offsets than the linear-combining receiver. It is also observed that for the linear-combining receiver, the optimum diversity order increases as the timing and frequency offset increases over both Rician-fading and Rayleigh-fading channels; however, the reverse is true for the product-combining receiver.

EXIT-Chart-Aided Three-Stage Concatenated Ultrawideband Time-Hopping Spread-Spectrum Impulse Radio Design

A serially concatenated and iteratively decoded irregular variable-length coding (IrVLC) scheme is amalgamated with a unity-rate precoded time-hopping (TH) pulse-position-modulation (PPM)-aided ultrawideband (UWB) spread-spectrum (SS) impulse radio design. The proposed design is capable of operating at low SNRs in Nakagami-m fading channels contaminated by partial band noise jamming (PBNJ) as a benefit of lossless IrVLC joint source and channel coding. Although this scheme may readily be used for lossless video or audio compression, for example, we only used it here for lossless near-capacity data transmission. A number of component variable-length-coding (VLC) codebooks having different coding rates are utilized by the IrVLC scheme for encoding specific fractions of the input source symbol stream. EXtrinsic Information Transfer (EXIT) charts are used to appropriately select these fractions to shape the inverted EXIT curve of the IrVLC and, hence, to match that of the inner decoder, which allows us to achieve an infinitesimally low bit error ratio (BER) at near-capacity SNR values.

Iterative Detection of Unity-Rate Precoded FFH-MFSK and Irregular Variable-Length Coding

Iterative decoding of an irregular variable-length coding (IrVLC) scheme concatenated with precoded fast frequency-hopping (FFH) M-ary frequency-shift keying (MFSK) is considered. We employ extrinsic information transfer (EXIT) charts to investigate the three-stage concatenation of the FFH-MFSK demodulator, the rate-1 decoder, and the outer IrVLC decoder. The proposed joint source and channel coding scheme is capable of operating at low signal-to-noise ratios (SNRs) in Rayleigh fading channels contaminated by partial-band noise jamming (PBNJ). The IrVLC scheme is composed of a number of component variable-length coding (VLC) codebooks employing different coding rates that encode particular fractions of the input source symbol stream. These fractions may be chosen with the aid of EXIT charts to shape the inverted EXIT curve of the IrVLC codec so that it can be matched with the EXIT curve of the inner decoder. We demonstrate that using the proposed scheme, an infinitesimally low bit error ratio (BER) may be achieved at low SNR values.

Joint iterative channel estimation and soft-chip combining for a MIMO MC-CDMA anti-jam system

Multicarrier code division multiple access (MCCDMA) systems using complex-quadratic spreading sequences and cyclic delay diversity (CDD) facilitate frequency or time domain chip combining to mitigate different types of jamming. In this paper, multiple-input multiple-output (MIMO) channel coefficients, jamming power, and jammer state information (JSI) are jointly estimated to suppress the adverse effects of partial-band noise jamming. We derive weighted least square error (LSE) and linear minimum mean square error (MMSE) channel estimators operating under jamming and investigate the constraints on the cyclic delays. The JSI for the pilot symbols is estimated to assist estimation of the time-varying frequency selective channel coefficients by updating the noise covariance matrix. We also derive the optimum (sufficient statistics) chip combining weights for the data symbols that require the JSI; hence, the JSI for the data symbols is iteratively estimated using the decoder output. Simulation results demonstrate that the proposed iterative despreading (includes JSI estimation and chip combining), demapping, and decoding receiver with soft- JSI-assisted channel estimation and chip combining is very robust against partial-band noise jamming.

Mellin-Transform-Based Performance Analysis of FFH $M$ -ary FSK Using Product Combining for Combatting Partial-Band Noise Jamming

We employ the Mellin transform to facilitate the bit error ratio (BER) analysis of a fast frequency hopping (FFH)-assisted, M-ary frequency-shift keying (MFSK) using product combining (PC) when the transmitted signal is subjected to both Rayleigh fading and partial-band noise jamming. Exploiting the fact that the Mellin transform of the product of independent random variables is the product of their Mellin transforms, we derive the probability density function (PDF) of the PC's output. The derivation of the PDF then allows the computation of the system's BER. It is shown that the Mellin transform substantially simplifies the analysis of the PC receiver and hence facilitates, for the first time, the analysis of the FFH-MFSK PC receiver for modulation orders of M > 2.

Antijamming Performance of Space-Frequency Coding in Partial-Band Noise

Space-frequency coded (SFC) orthogonal frequency-division multiple access (OFDMA) system is considered under partial band noise jamming (PBNJ). Analytical expressions for the bit error probability (BEP) are derived for OFDMA with and without SFC in a frequency-selective fading environment. It is shown that SFC increases the resistance of OFDMA against PBNJ and reduces the BEP considerably.

Performance of coherent fast frequency-hopped spread-spectrum receivers with partial-band noise jamming and AWGN

Performance analyses of coherent fast frequency-hopped spread-spectrum (FHSS) systems with the presence of partial-band noise jamming (PBNJ) and additive white gaussian noise (AWGN) are presented. Bit-error-rate expressions for the coherent maximum-likelihood (ML), linear-combination (LC), and hard-decision majority-vote (HDMV) receivers with binary phase-shift-keying are derived and validated by simulation results. Among the three proposed receivers, the coherent ML receiver gives the best performance under the worst-case PBNJ condition, followed by the coherent HDMV receiver and the coherent LC receiver. The BER results of the coherent ML receiver improve as the diversity level increases, although the incremental improvement in performance will diminish eventually when the diversity level is sufficiently large. The coherent LC receiver is incapable of providing diversity improvement under the worst-case PBNJ condition. For the coherent HDMV receiver it has been shown that there is an optimum diversity level under the worst-case PBNJ condition. The locus of the optimum diversity level for the coherent HDMV receiver is also presented, which allows one to obtain the optimum diversity level for the coherent HDMV receiver under different levels of signal-to-jamming ratio. It has been shown that the three coherent receivers significantly outperform the various existing noncoherent diversity-combining receivers under the worst-case PBNJ and AWGN conditions.

Iterative channel estimation and decoding for convolutionally coded anti-jam FH signals

An iterative algorithm for joint decoding and channel estimation in frequency-hopping (FH) networks is proposed. In the proposed algorithm, soft decoder outputs are used in the iterative estimation of the time-varying variance of the additive interference resulting from the sum of the thermal noise, partial-band noise jamming, and other-user interference. The soft outputs are also used in the estimation of the independent random carrier phases and multiplicative Rayleigh fading coefficients in different frequency dwells. The estimation process is further enhanced through the insertion of known symbols in the transmitted data stream. The proposed iterative symbol-aided demodulation scheme is compared with the coherent scenario, where the channel state information is assumed to be known a priori at the receiver, for both convolutionally coded and turbo coded FH systems. The proposed iterative channel estimation approach is suited for slow FH systems where the channel dynamics are much slower than the hopping rate. This observation motivates the consideration of another robust approach for generating the log-likelihood ratios for fast hopping systems in additive white Gaussian noise channels. Simulation results that demonstrate the excellent performance of the proposed algorithms in various scenarios are also presented.

Error probabilities of an FFH/BFSK self-normalizing receiver in a Rician fading channel with multitone jamming

We derive the analytical bit-error rate (BER) expressions for a fast frequency-hopped binary frequency-shift keying self-normalizing receiver over a fading channel with the worst-case band multitone jamming (MTJ) and additive white Gaussian noise (AWGN). The desired signal and MTJ are assumed to undergo independent Rician fading and our analyses, validated with simulation results, show that the system performance is not sensitive to different types of MTJ fading conditions. The self-normalizing receiver is found to be superior to the linear-combining receiver when the signal amplitude does not experience severe fading, while the converse is true under Rayleigh fading signal conditions. Under a Rician fading channel and AWGN conditions, the worst-case MTJ and the worst-case partial-band noise jamming are shown to have similar effects on the BER performance of the self-normalizing receiver with diversity.

Rejection of partial-band noise jamming with FFH/BFSKproductcombining receiver over Nakagami-fading channel

The bit error rate performance of a noncoherent fast frequency-hopping binary frequency shift keying system equipped with a product combining receiver is evaluated in the presence of partial-band noise jamming and additive white Gaussian noise over a Nakagami-faded channel. Using the derived output characteristic function, numerical results are generated for different fading conditions.

Worst-case partial-band noise jamming of Rician fading channels

Analyses of worst-case partial-band noise jamming of binary digital modulation are presented. Both noncoherent detection and differentially coherent detection over slowly varying, frequency-nonselective Rician fading channels are considered. The analysis bridges the gap between earlier works by Viterbi and Jacobs (1975) and by Omura (1981) for the limiting cases of Gaussian and Rayleigh channels, respectively. The results complement those by Crepeau (1990) for noncoherent binary transmission over the Nakagami fading channel. However, the Rician channel model has more physical significance since the parameter k is the ratio of scattered and specular powers. It is shown that a partial-band (partial-time) jamming strategy is optimum for all Rician channels with k<1 if the signal-to-jamming power ratio is sufficiently high. On the other hand, a full-band jamming strategy is the optimal strategy for k/spl ges/1. Results for the Gaussian and Rayleigh channels can be derived from the present analysis in the limit as k=0 and k/spl rarr//spl infin/, respectively.

Effects of fading and partial-band noise jamming on a fast FH/BFSK acquisition receiver with noise-normalization combination

We present the performance analysis of a fast frequency-hopped (FH) binary orthogonal frequency-shift keying acquisition receiver for communication against adverse environments. The receiver employs noncoherent, noise-normalized, matched-filtered (MF) correlation detection for rapid acquisition in the search mode. Our analysis includes four types of communication environments, namely additive white Gaussian noise (AWGN) channel, AWGN channel with partial-band noise jamming, fading channels, and fading channels with partial-band noise jamming. The considered fading channels include Nakagami-m, Rician, and Rayleigh amplitude models. Based on Beaulieu's (see ibid., vol.38, no.9, p.1463, 1990) convergent series approach, efficient analytical formulas are developed for performance evaluation. Example performance results for various environments are presented in terms of two acquisition probabilities, namely the detection probability and the false alarm probability of the noise-normalized MF detector. It is analytically shown that with a short MF correlation length and with a sufficiently large ratio of signal power to noise power the fast FH diversity combining yields noticeable performance improvement for environments with strong fading. When the MF correlation is lengthened, this improvement tends to fade away and the diversity combining results in performance loss.

Analysis of triple dwell-time acquisition scheme for frequency-hopped spread spectrum signals

A serial-search frequency-hopped acquisition scheme that employs a triple dwell-time with binary integration (TDT/BI) is analysed. The probability density function, characteristic function and mean value of the random acquisition time for this scheme are obtained. Moreover, the performance of the TDT/BI acquisition scheme is established in partial-band noise jamming and partial-band tone jamming in addition to additive white gaussian noise environments. Results indicate that the TDT/BI acquisition scheme outperforms the double dwell-time with binary integration (DDT/BI) acquisition scheme at relatively high jamming-to-signal ratios (JSR). Thus, in the presence of tone jamming, the TDT/BI acquisition scheme features a mean acquisition time that is 0·2 times faster than that of the DDT/BI scheme at JSR= 12dB; while in the presence of noise jamming the TDT/BI acquisition scheme is about 0·6 times faster than the DDT/BI scheme at the same JSR.

System optimization and experimental performance of two serial-search acquisition schemes for FH spread spectrum signals

System optimization is carried out for fixed dwell-time with false alarm memory (FDT/FAM) and double dwell-time with binary integration (DDT/BI) acquisition schemes for FH spread spectrum signals. System optimization includes two important parameters of the acquisition schemes: the number of sweeps of the employed search strategy and the threshold setting. Furthermore, optimization of these parameters is carried out in three different environments: additive white Gaussian noise (AWGN), partial band noise jamming and partial band tone jamming. The performances of the FDT/FAM and DDT/BI acquisition schemes are compared with the performance of the FDT acquisition scheme. A microprocessor-based experimental system is designed and implemented. This system is then used to simulate FDT, FDT/FAMB and DDT/BI acquisition schemes for evaluation purposes. Experimental results for the three acquisition schemes in different communication environments are obtained, they compare very well with theoretical results.

Neural network applications for jamming state information generator

A known jamming state information (JSI) scheme for a coded frequency-hopped M-ary frequency-shift-keying (FH/MFSK) system under partial-band noise jamming, plus additive white Gaussian noise, utilizes the maximum a posteriori (MAP) rule based on the total energy received in the M-tone signaling bands. It is assumed that the knowledge of partial-band noise jamming fraction is available to the JSI generator. Because this scheme reduces the M-dimensional information into one dimension, i.e., the total energy, the generated JSI may not be the best. In this paper, a neural network approach to the JSI generation is presented. The efficiency of the new JSI generator with known partial-band noise jamming fraction is compared with the MAP generator. The neural network scheme is then generalized to increase its robustness by allowing for an unknown partial-band noise jamming fraction. The neural network JSI generator with or even without knowledge of jamming fraction offers significantly better performance for a coded FH/MFSK communication system than the MAP JSI generator for high code rate.

Performance analysis of a slow FH/MFSK acquisition scheme in random partial band noise jamming

A post-detection-combining matched-filter scheme for coarse acquisition of slow frequency hopping/multiple frequency shift keying signals, based on a convergent infinite series approach, is analysed. An analytical formula is developed which characterises acquisition performance both in a benign broadband Gaussian noise channel and in an adverse environment containing random partial-band noise jamming. Detection and false alarm probabilities are evaluated for various jamming conditions. It is shown that the scheme is relatively insensitive in miss detection performance, while vulnerable in false alarm performance, to jamming. By increasing the number of largest squared envelopes combined or by widening the spread-spectrum band, a significant improvement in performance of the worst case can be achieved.

Performance analysis of two serial-search acquisition schemes for FH spread spectrum signals

Initial synchronization (acquisition) schemes of frequency hopped (FH) spread spectrum signals often make use of serial-search acquisition techniques. Two FH serial-search acquisition schemes are introduced and analysed. These schemes are the fixed dwell-time with false alarm memory (FDT/FAM) and the double dwell-time with binary integration (DDT/BI) scheme. Statistical properties namely, probability density function, characteristic function and mean value of the random acquisiton time of each acquisition scheme are obtained. The performances of the FDT, FDT/FAM and DDT/BI acquisition schemes are established and compared in the presence of partial band noise jamming, partial band tone jamming and additive white gaussian noise (AWGN). The results indicate that the DDT/BI acquisition scheme outperforms the FDT and FDT/FAM acquisition schemes.

Design and analysis of a fast frequency-hopped DBPSK communication system. I. Error performance in AWGN plus partial-band noise jamming

The purpose of the paper is to present the design and performance analysis of a fast frequency-hopped (FFH) spread spectrum communication system employing differential binary phase-shifted-keying (DBPSK) modulation and differentially coherent demodulation. The receiver utilizes a hop time tracking loop to lock the hop clock. The authors present an analysis of the average bit error probability of the overall system when it is operating in additive white Gaussian noise plus partial-band noise jamming. The effect of channel phase distortion is also studied. >

Performance of robust metrics with convolutional coding and diversity in FHSS systems under partial-band noise jamming

The performance of robust metrics (metrics that can be computed from the outputs of the matched filters only) with convolutional coding and diversity under worst-case partial-band noise jamming is analyzed. Both binary and dual-k convolutional codes employing these metrics with diversity are compared via Union-Chernoff bounds. The performances of metrics considered in the literature that assume perfect side-information are given for comparison purposes. It is found that there exist very good robust metrics that provide performance comparable to metrics using perfect side-information. Among the robust metrics considered, the self-normalized metric offers the best performance and achieves performance practically identical to that of the square-law-combining metric with perfect side-information for M=8. >

Limiter-differential detection of a frequency-hopped CPFSK diversity system in partial-band jamming

The error probability achieved by a differential detector with a bandpass limiter preceding the receiver is analyzed for a slow-frequency-hopped CPFSK diversity waveform transmitted over a partial-band noise jamming channel, and is compared to the system's performance without the bandpass limiter. The system's thermal noise is not neglected in the analysis. In principle, each bit is repeated on L different hops, and for the FH/CPFSK system analyzed, these repetitions are combined to yield a soft decision. The main result is that a diversity gain for error rate improvement in worst-case partial-band jamming is realized with the detector preceded by a limiter, but not without the limiter. This is shown by considering the error probability for L=2 in comparison with that for L=1.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>