Noncoherent Frequency Research Articles

Quasi-FM Waveform Using Chaotic Oscillator for Joint Radar and Communication Systems

The authors propose a novel signal design for generating wideband quasi-Frequency Modulated (FM) waveforms using chaotic systems. The receiver is based on a self synchronizing chaotic system, making for fast synchronization that is robust to timing errors or Doppler shifts. The chaotic oscillator has fast and slow time scales, and the slow oscillating part of the chaotic system is used to sweep the fast oscillating part thereby generating a modulated waveform that changes its frequency as a function of time. The potentials of these waveforms are demonstrated for joint radar-communication (RadComm) systems. Using the same nonlinear system a chaos frequency shift keying (CFSK) approach is utilized to encode the digital information. To decode the information, a drive-response synchronization scheme is utilized. Results indicate that our proposed signal design closely matches the bit-error rate (BER) of theoretical noncoherent frequency shift keying (FSK) while having good radar imaging capabilities.

On the ASER performance of SC receiver with RQAM and HQAM over [formula omitted]-[formula omitted] fading

In this paper, we consider a multi-branch selection combining receiver over independent and non-identically distributed κ-μ fading channels. We derive new exact expressions for moment generating function of output signal-to-noise-ratio (SNR), average symbol error rate (ASER) of coherent rectangular and hexagonal quadrature amplitude modulations, and ASER of non-coherent frequency shift-keying modulation schemes. Further, an asymptotic ASER expression is also derived to determine the diversity order of the system. The analytical results are validated using Monte-Carlo simulations for a wide range of SNRs and fading parameters. Finally, the impact of channel parameters and the number of branches on the ASER performance is also studied.

Research on the system performance of SAC-FBGs codec scheme

The theory of codec based on non-coherent frequency domain codec (FBGs) and non-coherent spectral domain codec (SAC-FBGs) of light-brain grating is theoretically analyzed and its transmission performance is verified. The codec scheme with better performance is compared. An optical quadrature cyclic shift code with a code length N of 13, code weight ω of 4, and self-correlation λ of 1 is used to implement codec schemes using FBGs codec and SAC-FBGs codec, respectively. Based on multiple access interference, signal to interference ratio (SIR) and bit error rate (BER) are discussed separately. From experimental results, it can be concluded that under the condition that the optical orthogonal codes are identical and the number of concurrent users is the same, the signal to interference ratio of the OCDMA system obtained by using the SAC-FBGs coding and decoding scheme is higher than that of the OCDMA system obtained by using the FBGs coding and decoding scheme. The SIR has increased by nearly two orders of magnitude, and the multiple-site interference BER has decreased by 20 or even 100 orders of magnitude. The experiment verifies that the transmission performance of the same optical orthogonal code using the SAC-FBGs coding and decoding scheme is obviously higher than that of the system transmission performance using the FBGs coding and decoding scheme.

Multiple Range and Vital Sign Detection Based on Single-Conversion Self-Injection-Locked Hybrid Mode Radar With a Novel Frequency Estimation Algorithm

This article presents a single-conversion self-injection-locked (SIL) (SCSIL) hybrid mode radar with a novel frequency estimation algorithm, which improves the range resolution in a frequency-modulated continuous-wave (FMCW) mode and simultaneously detects the vital signs of multiple subjects in the CW mode. The system architecture includes an SIL oscillator (SILO), a frequency converter, two antennas, and a noncoherent frequency demodulator. Due to the frequency–phase relationship in the spectrum of the beat signal in the FMCW mode, the distance to the closely spaced subjects can be determined. Moreover, the algorithm will identify the most dominant component and remove it from the input signal, and the steps are repeated until the residual-to-input energy ratio is less than the threshold value. This iterative method can thus distinguish multiple signals whose frequencies are close to each other and can support a superresolution analysis in both FMCW and CW modes. In an experiment, the radar with a 150-MHz bandwidth and a sensing period of 20 s can simultaneously provide accurate range and vital sign information of two adjacent subjects with radial and azimuth spacings of 60 cm and 5°, respectively.

Improving reliability and latency of Wireless Sensor Networks using Concurrent Transmissions

Abstract Concurrent Transmissions (CT) based flooding appears as a highly reliable and low latency mechanism to achieve source-to-sink communication of packets within a Wireless Sensor Network (WSN). CT are usually misunderstood, since they are mainly analyzed in the baseband domain. A comprehensive analysis, including the effects of the carrier, demonstrates that they cannot work in simple phase-modulated communication systems due to the beating effect. In contrast, non-coherent frequency receivers offer a very robust behavior. CT applicability in IEEE 802.15.4 is mainly because of two factors: transmissions are usually demodulated as non-coherent MSK (as opposed to coherent OQPSK) and the Direct Sequence Spread Spectrum (DSSS), that helps minimizing the error rate.

CDF and MGF based analysis over Rayleigh TWDP shadowed fading channel for indoor communication

ABSTRACTRecently, the two-wave with diffuse power (TWDP) distribution has been extensively used to model the shadowing in multipath-faded/shadowed indoor environment. In this article, novel expressions for joint moments, mean, second moment, variance and cumulative distribution function for Rayleigh TWDP shadowed fading model are derived. By using the derived expression of mean and variance, the expression for amount of fading is obtained. Also, the outage probability, moment generating function and average bit error rate (ABER) for various modulation schemes namely binary phase shift keying (BPSK), binary frequency shift keying (BFSK), minimum shift keying (MSK), differentially coherent phase shift keying (DCPSK) and non-coherent frequency shift keying (NCFSK) are calculated. The derived expressions for cumulative distribution function, outage probability and ABER are presented in analytical format and have been numerically evaluated. Moreover, the numerical results of ABER using MSK and DPSK modulation schemes is compare with results of Rayleigh Gamma composite fading model. The study shows that better outage probability (0.01) is observed at 40dB average signal to noise ratio (SNR) with 5dB lowest threshold SNR, however, at higher threshold SNR (>5dB) with fixed average SNR (40dB), poor outage probability performance are obtained. Further, at higher shadowing (10dB), for fixed average SNR (15dB), minimum error probability (10−4) is observe, while at lower shadowing (less than 10dB), higher error probability (greater than 10−4) is observed that represents poor BER performance.

Ambiguity Function Analysis for OFDM-Based LDACS Passive Multistatic Radar

The ambiguity function analysis is central to investigating the resolution capabilities of a radar system. It is particularly important for passive radar scenarios, where the signals of opportunity have not been originally designed for radar purposes. This paper focuses on studying the achievable resolution capabilities for a noncoherent orthogonal frequency division-multiplexing (OFDM)-based passive multistatic radar for L-band digital aeronautical communication system (LDACS) signals. For this purpose, the ambiguity function obtained when employing the OFDM-based LDACS communications signals as signals of opportunity is studied. A generic bistatic link is considered and closed-form expressions for the expectation of the corresponding ambiguity function when accounting for the different signal contributions are derived. The resulting expressions are then used to evaluate and analyze the overall multistatic radar ambiguity function for two sample radar scenarios. The results highlight the impact of the geometry on the shape of the ambiguity function, allowing therefore for a better understanding of the effect that the geometry has on the range and velocity resolution capabilities of the studied system.

Analysis of Error Rate Performance Limit of DBPSK/NCFSK Modulations for OFDM System with MRC Diversity in Correlated Nakagami-m Fading Channels

In this paper, we derive exact and asymptotic bit error rate (BER) formulas of differential binary phase shift keying (DBPSK) and non-coherent frequency shift keying (NCFSK) modulations for orthogonal frequency division multiplexing (OFDM) system employing maximal ratio combining (MRC) receive diversity technique, especially over correlated Nakagami-m fading channels. In particular, exploiting the derived asymptotic BER formulas, asymptotic modulation gain and diversity order can be subsequently achieved, which enable us to easily predict the performance limit of the considered system and channel environments. Based on our asymptotic analysis, we can also analytically demonstrate the asymptotic SNR performance gap between DBPSK and NCFSK.

Energy consumption analysis of modulation schemes in IEEE 802.15.6-based wireless body area networks

Selection of the most energy-efficient modulation scheme is vital for wireless body area networks (WBANs) for improving the network lifetime. In this paper, we investigate the performance of various modulation schemes specified by IEEE 802.15.6 WBAN standard, in terms of energy consumed for successfully transferring one packet from the sensor node to the hub. Assuming a contention-free MAC protocol, we present an analytical model for computing the energy consumption for a given modulation scheme both for uncoded transmission as well as transmission using Bose-Chaudhuri-Hocquengham (BCH) codes; the coding scheme specified by IEEE 802.15.6 for WBAN. The following communication scenarios specific to a WBAN are considered: (i) in-body communication between invasive devices and hub and (ii) on-body communication among non-invasive devices and hub with line-of-sight (LOS) and non-LOS (NLOS) channels. The results show that the use of higher order differential phase shift keying (D8PSK)-based modulation schemes results in significant reduction of total energy consumption. When BCH codes with various code rate specifications are used, total energy consumption remains lower for the higher order modulation schemes. The energy consumption is further reduced when non-coherent frequency shift keying (NC-MFSK) is employed as an alternate modulation scheme instead of differential PSK schemes.

BER performance and data throughput of body sensor networks for reliable biological signal transmission over the human body

According to the IEEE 802.15 task group 6, human body communication (HBC) is a wireless body area network (WBAN) that operates at frequency band 5–50 MHz. In particular, communication between nodes is through body surface to body surface, and the human body acts as the transmission channel. This paper designs the link budget signaling parameters required for reliable transmission of biological signals over the IEEE 802.15.6a HBC channel model, and investigates the bit-error-rate (BER) and data throughput performances of different modulation schemes. These modulation schemes include non-coherent binary frequency shift keying (NcBFSK) with non-coherent detection, in addition to the commonly used schemes for HBC communications, namely coherent binary phase shift keying (CBPSK), coherent binary frequency shift keying (CBFSK), and on-off keying (OOK). According to the numerical results based on theoretical analysis, experimental results, as well as Monte-Carlo simulations, NcBFSK with non-coherent detection and bandwidth-integration window product , CBPSK, CBFSK, and OOK, represent appropriate solutions for the reliable transmission of biological signals over HBC-based WBANs. The results are based on and 1 Mbps data rate for low data rate applications, and and data rate = 10 Mbps for high data rate applications.

The Effects of Multiple Carrier Frequency Offsets on the Performance of Virtual MISO FSK Systems

In this letter, a virtual multiple-input single-output (VMISO) network employing non-coherent frequency shift keying (FSK) is considered. In the VMISO network, spatially separated single-antenna nodes transmit the same information cooperatively to a single receiver where each received signal is affected by an independent carrier frequency offset (CFO). The existing works in this area assume a perfect carrier synchronization between the nodes. However, in this letter, the effects of CFOs on the performance degradation of this network are analyzed. For that purpose, the expression for the probability of symbol error has been derived. The results indicate that the performance is degraded due to CFOs, which is dependent upon the magnitude of CFOs, signal-to-noise ratio (SNR), number of transmitting nodes, and the modulation order of FSK. At high SNR, the CFOs affect the system severely and the performance margin is minimum.

Adaptive Jamming Suppression in Coherent FFH System Using Weighted Equal Gain Combining Receiver over Fading Channels with Imperfect CSI

Fast frequency hopping (FFH) is commonly used as an antijamming communication method. In this paper, we propose efficient adaptive jamming suppression schemes for binary phase shift keying (BPSK) based coherent FFH system, namely, weighted equal gain combining (W-EGC) with the optimum and suboptimum weighting coefficient. We analyze the bit error ratio (BER) of EGC and W-EGC receivers with partial band noise jamming (PBNJ), frequency selective Rayleigh fading, and channel estimation errors. Particularly, closed-form BER expressions are presented with diversity order two. Our analysis is verified by simulations. It is shown that W-EGC receivers significantly outperform EGC. As compared to the maximum likelihood (ML) receiver in conventional noncoherent frequency shift keying (FSK) based FFH, coherent FFH/BPSK W-EGC receivers also show significant advantages in terms of BER. Moreover, W-EGC receivers greatly reduce the hostile jammers’ jamming efficiency.

Study of PCM/FM Telemetry Sequence Soft Demodulation

In order to improve the performance of PCM/FM signal demodulation system, this paper studies a kind of Symbol Detection more (Multi-Symbol Detection, MSD) technology. First for PCM/FM in hardware demodulation, a series of problems in the introduction of MSD software demodulation method; Then the MSD demodulation under low SNR synchronous implementation; The algorithm simulation, the results show that the bit error rate of 10-4, detection performance than traditional non-coherent frequency discrimination algorithm can improve the nearly 3 dB, the performance is very ideal.

Calculating the probability of error per symbol on the basis of MGF method using Rician fading for MFSK

In this paper is presented how to calculate the probability of error per symbol of M-ary non-coherent frequency modulation (M-ary Frequency Shift Keying, MFSK) over a slow, flat, identically independently distributed Rician fading channels. SEP is calculated by technique with maximal ratio combining diverzity, using the moment generating function. We assume that the information is known on the receiving side of the channel. Probabilities of error per symbol for the modulation technique are plotted for different values of Rician factor K, diverzity order N and modulation order M.

SNR Estimation for Non-Coherent M-FSK Receivers in Rice Fading Environment

The problem of estimating the average signal-to-noise ratio (SNR) in a non-coherent M-ary frequency shift keying (NCMFSK) receiver has been considered, where the transmitted signal is propagated over a noisy Ricean fading channel. Closed-form maximum likelihood estimators for both the data-aided and non data-aided scenarios have been derived using the approximations of the modified Bessel functions. Numerical results are presented and the performance of the estimators is evaluated by comparing with a Cramer-Rao bound.

SNR Estimation for M-ARY Non-Coherent Frequency Shift Keying Systems

This paper considers how to estimate the average signal-to-noise ratio (SNR) for a communication system employing orthogonal non-coherent M-ARY frequency shift keying (NCMFSK), in white Gaussian noise (AWGN) and over both symbol-by-symbol fading channels and block fading channels. The proposed algorithm finds its application in a variety of applications including a cooperative transmission system, which is the main motivation behind this study. The maximum likelihood estimator and one using data statistics have been derived and simulated for various scenarios including data-aided, non-data aided and joint estimation using both the data and pilot sequences. We also derive the Cramer-Rao bound for the estimators in the case of Rayleigh fading channels. The results show that for a particular region of interest (e.g. high SNR or low SNR) and depending upon the availability of pilot sequence, a particular SNR estimation scheme is suitable.

Tight lower bound of optimal non-coherent detection for FSK modulated AF cooperative communications in Rayleigh fading channels

When wireless channels undergo fast fading, non-coherent frequency shift keying (FSK) (de)modulation schemes may be considered for amplify-and-forward (AF) cooperative communications. In this paper, we derive the bit-error-rate performance of partial non-coherent receiver as a lower bound of the optimal non-coherent receiver for FSK modulated AF cooperative communications. From the simulation and analytical results, it is found that the derived lower bound is very closed to simulation results. This result shows that knowing partial channel state information may not improve system performance significantly. On the other hand, conventional optimal non-coherent receiver involves complicated integration operation. To address the above complexity issue, we also propose a near optimal non-coherent receiver which does not involve integration operation. Simulation results have shown that the performance gap between the proposed near optimal receiver and the optimal receiver is small.

A New Soft-Fusion Approach for Multiple-Receiver Wireless Communication Systems

In this paper, a new soft-fusion approach for multiple-receiver wireless communication systems is proposed. In the proposed approach, each individual receiver provides the central receiver with a confidence level rather than a binary decision. The confidence levels associated with the local receiver are modeled by means of soft-membership functions. The proposed approach can be applied to wireless digital communication systems, such as amplitude shift keying, frequency shift keying, phase shift keying, multi-carrier code division multiple access, and multiple inputs multiple outputs sensor networks. The performance of the proposed approach is evaluated and compared to the performance of the optimal diversity, majority voting, optimal partial decision, and selection diversity in case of binary noncoherent frequency shift keying on a Rayleigh faded additive white Gaussian noise channel. It is shown that the proposed approach achieves considerable performance improvement over optimal partial decision, majority voting, and selection diversity. It is also shown that the proposed approach achieves a performance comparable to the optimal diversity scheme.

Soft Metrics and EXIT Chart Analysis of Noncoherent MFSK with Diversity Reception in Rician Fading Channel

A convolutionally encoded noncoherent M-ary Frequency Shift Keying (MFSK) modulation scheme with diversity reception is considered. Soft metrics for Soft Decision Decoding (SDD) of noncoherent MFSK are derived assuming Rician channel model. Furthermore, the convergence behavior of the MFSK receiver is investigated using EXtrinsic Information Transfer (EXIT) charts. It has been demonstrated that the derived expressions for soft information are useful allowing SDD of the MFSK scheme exploiting diversity and the EXIT chart analysis provides useful insights into its iterative decoding behavior.

A Unified Framework for Interference Analysis of Noncoherent MFSK Wireless Communications

This paper presents a new unified analytical technique for accurate interference analysis of noncoherent M-ary frequency shift keying (MFSK) wireless communication systems in the presence of additive white Gaussian noise (AWGN) and multiple arbitrary interfering signals. New exact bit error rate expressions are derived for nonorthogonal noncoherent binary FSK in the presence of an arbitrary number of interfering signals having arbitrary spectral shapes at arbitrary frequency offsets. Furthermore, tight upper bounds for the symbol and bit error rates are given for noncoherent MFSK with arbitrary tone spacings. These results are extended to include MFSK signals experiencing Rayleigh, Nakagami-m or Rician fading. Some specific interference scenarios are analyzed in details, including jammers with a given Doppler-spread, direct sequence spread spectrum and orthogonal frequency division multiplexing signals, and a Poisson field of arbitrary interferers.