Noncoherent Frequency Shift Keying Research Articles

Performance analysis of energy harvesting‐enabled relay networks inκ‐μfading channels

AbstractIn this paper, we investigate the performance of an energy harvesting (EH)‐enabled multiple relay network operating over generalized‐fading channels. Our approach involves utilizing a partial relay selection strategy and employing an amplify and forward relay protocol for efficient EH from RF signals. Additionally, we integrate a selection combining scheme at the receiver to combine both direct and relaying path signals. In our research, we first obtain the exact closed‐form expression of the cumulative distribution function (CDF) for the system under investigation. Subsequently, we derive expressions for the outage probability (OP) and the moment generating function (MGF) using the derived CDF expression. Furthermore, with the assistance of a CDF‐based approach, we derive closed‐form expressions for the average symbol error rate (ASER) for coherent quadrature amplitude modulation (QAM) schemes, including rectangular QAM (RQAM) and hexagonal QAM (HQAM). We also analyze the ASER expression for non‐coherent frequency shift keying (NCFSK), leveraging the derived MGF expression. To gain valuable insights into the performance of EH‐enabled multiple relay networks, we assess the asymptotic expression of the OP. The outcomes indicate how the behavior of the system is affected by various factors such as time switching ratio, channel fading components, number of relays, and the distance between nodes. To corroborate the accuracy of the analytical findings, Monte Carlo simulations are executed.

Noncoherent Frequency-Shift Keying for Ambient Backscatter Over OFDM Signals

Noncoherent Frequency-Shift Keying for Ambient Backscatter Over OFDM Signals

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.

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.

Noncoherent LDPC-Coded Physical-Layer Network Coding Using Multitone FSK

A noncoherent two-way relaying system is developed using physical-layer network coding for improved throughput over conventional relaying in a fading channel. Energy-efficient noncoherent operation is achieved using multitone frequency shift keying (FSK). A novel soft-output demodulator is developed for the relay, and corresponding achievable exchange rates are found for Rayleigh fading and AWGN channels. Bit-error rate performance approaching the achievable rate is realized using a capacity-approaching channel code and a receiver architecture, which iterates between demodulation and channel decoding. Iterative decoding is performed feeding information back from the channel decoder to the demodulator. In addition, the error-rate performance is made to approach the achievable rate more closely by optimizing LDPC codes for this system. The energy efficiency improvement obtained by increasing the modulation order is more dramatic for the proposed physical-layer network coding scheme than it is for a conventional point-to-point system. Using optimized LDPC codes, the bit-error rate performance is improved by as much as 1.1 dB over a widely known standardized LDPC code, and comes to within 0.7 dB of the limit corresponding to the achievable rate. Throughout this paper, the performance for physical-layer network coding is compared with conventional network coding. When noncoherent FSK is used, physical-layer network coding enables higher achievable rates, and conventional network coding exhibits better energy efficiency at low rates.

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.

Log-Linear-Complexity GLRT-Optimal Noncoherent Sequence Detection for Orthogonal and RFID-Oriented Modulations

Orthogonal modulation, for example, frequency-shift keying (FSK) or pulse-position modulation (PPM), is primarily used in relatively-low-rate communication systems that operate in the power-limited regime. Optimal noncoherent detection of orthogonally modulated signals takes the form of sequence detection and has exponential (in the sequence length) complexity when implemented through an exhaustive search among all possible sequences. In this work, for the first time in the literature, we present an algorithm that performs generalized-likelihood-ratio-test (GLRT) optimal noncoherent sequence detection of orthogonally modulated signals in flat fading with log-linear (in the sequence length) complexity. Moreover, for Rayleigh fading channels, the proposed algorithm is equivalent to the maximum-likelihood (ML) noncoherent sequence detector. Simulation studies indicate that the optimal noncoherent FSK detector attains coherent-detection performance when the sequence length is on the order of 100, offering a 3–5 dB gain over the typical energy (single-symbol) detector. While the conventional exhaustive-search approach becomes infeasible for such sequence lengths, the proposed implementation requires a log-linear only number of operations, opening new avenues for practical deployments. Finally, we show that our algorithm also solves efficiently the optimal noncoherent sequence detection problem in contemporary radio frequency identification (RFID) systems.

Noncoherent Relaying in Energy Harvesting Communication Systems

In energy harvesting (EH) relay networks, the coherent communication requires accurate estimation/tracking of the instantaneous channel state information (CSI) which consumes extra power. As a remedy, we propose two noncoherent EH relaying protocols based on the amplify-and-forward (AF) relaying, namely, power splitting noncoherent AF (PS-NcAF) and time switching noncoherent AF (TS-NcAF), which do not require any instantaneous CSI. We develop a noncoherent framework of simultaneous wireless information and power transfer (SWIPT), embracing PS-NcAF and TS-NcAF in a unified form. For arbitrary $M$ -ary noncoherent frequency-shift keying (FSK) and differential phase-shift keying (DPSK), we derive maximum-likelihood detectors (MLDs) for PS-NcAF and TS-NcAF in a unified form, which involves integral evaluations yet serves as the optimum performance benchmark. To avoid expensive integral computations, we propose a closed-form detector using the Gauss-Legendre approximation, which achieves almost identical performance as the MLD but at substantially lower complexity. These EH-based noncoherent detectors achieve full diversity in Rayleigh fading. Numerical results demonstrate that our proposed PS-NcAF and TS-NcAF may outperform the conventional grid-powered relay system under the same total power constraint. Various insights which are useful for the design of practical SWIPT relaying systems are obtained. Interestingly, PS-NcAF outperforms TS-NcAF in the single-relay case, whereas TS-NcAF outperforms PS-NcAF in the multi-relay case.

Energy Harvesting Noncoherent Cooperative Communications

This paper investigates simultaneous wireless information and power transfer (SWIPT) in energy harvesting (EH) relay systems. Unlike the existing SWIPT schemes requiring the instantaneous channel state information (CSI) for coherent information delivery, we propose a noncoherent SWIPT framework for decode-and-forward (DF) relay systems bypassing the need for the instantaneous CSI and consequently saving energy in the network. The proposed SWIPT framework embraces both the power-splitting noncoherent DF (PS-NcDF) and timeswitching noncoherent DF (TS-NcDF) in a unified form, and supports arbitrary M-ary noncoherent frequency-shift keying (FSK) and differential phase-shift keying (DPSK). The exact (noncoherent) maximum-likelihood detectors (MLDs) for PS-NcDF and TS-NcDF are derived in a unified form, which involves integral evaluations yet serves as the optimum performance benchmark for noncoherent SWIPT. To reduce the computational cost of the exact MLDs, we also propose closed-form approximate MLDs achieving near-optimum performance, thus serving as a practical solution for noncoherent SWIPT. Numerical results demonstrate a performance tradeoff between the first and second hops through the adjustment of time switching or power splitting parameters, whose optimal values minimizing the symbol-error rate (SER) are strictly between 0 and 1. We demonstrate that M-FSK results in a significant energy saving over M-DPSK for M ≥ 8; thus M-FSK may be more suitable for EH relay systems.

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.

Performance of a Free-Space-Optical Relay-Assisted Hybrid RF/FSO System in Generalized <inline-formula> <tex-math notation="LaTeX">$M$</tex-math> </inline-formula>-Distributed Channels

This paper investigates the average symbol error rate (ASER) performance of a dual-hop hybrid relaying system relying on both radio frequency (RF) and free space optical (FSO) links. Specifically, the RF link is used for supporting mobile communication, while the FSO link is adopted as the backhaul of the cellular infrastructure. Considering non-line-of-sight (NLoS) RF transmissions and a generalized atmospheric turbulence (AT) channel, the associated statistical features constituted of both the exact and the asymptotic moment generating functions (MGF) are derived in closed form. They are then used for calculating the ASER of M-ary phase shift keying (PSK), differentially encoded non-coherent PSK (DPSK) and non-coherent frequency-shift keying (FSK). A range of additional asymptotic expressions are also derived for all the modulation schemes under high signal-to-noise ratios (SNR). It is observed from the asymptotic analysis that the ASERs of all the modulation schemes are dominated by the average SNR of the RF link in the hybrid relaying system using a fixed relay gain, while in the relaying system using a dynamic channel dependent relay gain, the ASERs of all the modulation schemes depend both on the average SNR and on the AT condition of the FSO path. We also find that the fixed-gain relaying strategy achieves twice the diversity order of the channel-dependent relaying strategy albeit at the cost of requiring a high power amplifier (PA) dynamic range at the relay node. Furthermore, by comparing the asymptotic ASERs, we calculate the SNR differences between the different modulation schemes in both the fixed-gain and the channel-dependent relaying system. Finally, simulation results are presented for confirming the accuracy of our expressions and observations.

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.

Approximation to independent lognormal sum with α–μ distribution and the application

This paper considers the statistical distribution of the sum of independent and possibly non-identically distributed lognormal random variables (RVs). The α–μ distribution is employed to approximate the probability of density function (PDF) of the lognormal sum. Two approaches, e.g., the moment-based and non-linear least square based (LS-based) methods, are used to obtain the parameters of α–μ distribution. Accounting for maximal-ratio combining (MRC) receiver, an analytical expression of the average bit error probability (ABEP) of the M-ary noncoherent frequency-shift keying (M-NFSK) modulation is derived. Finally, the performances of the α–μ approximation and the ABEP are evaluated via numerical experiments.

Exact BER Performance Analysis of Link Adaptive Relaying with Noncoherent BFSK Modulation

Link adaptive relaying (LAR) is one of the most popular techniques developed for mitigating error propagation in decode and forward (DF) based cooperative wireless networks which employs soft power scaling approaches at the relay nodes. On the other side, frequency shift keying (FSK) is a prominent technique for eliminating the need for channel estimation by training sequences which increases complexity of the system and causes reduction in the transmission rate in proportional to the number of users involved in the network. In this paper, performance of an LAR scheme with noncoherent binary FSK (BFSK) signaling is investigated by deriving exact closed form bit error rate expressions in Rayleigh fading channels.

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.

Subcarrier Intensity Modulated Optical Wireless Communications in Atmospheric Turbulence With Pointing Errors

An optical wireless communication system using subcarrier intensity modulation is analyzed for gamma-gamma turbulence channels with pointing errors. We study the error rate performance of such a system employing M-ary phase-shift keying, differential phase-shift keying, and noncoherent frequency-shift keying. Highly accurate error rate approximations are derived using a series expansion approach. Furthermore, outage probability expressions are obtained for such a system. Asymptotic error rate and outage probability analyses are also presented. Our asymptotic analysis reveals some unique transmission characteristics of such a system. Our findings suggest that pointing error compensation is necessary as pointing errors can severely degrade the error rate and outage probability performance of an uncompensated system.

Optical Communication Using Subcarrier Intensity Modulation in Strong Atmospheric Turbulence

Error rate performance of subcarrier intensity modulations is analyzed for optical wireless communications over strong atmospheric turbulence channels. We study the error rate of a subcarrier intensity modulated optical wireless communication system employing M -ary phase-shift keying, differential phase-shift keying, and noncoherent frequency-shift keying. Both K -distributed turbulence channel (strong) and negative exponential turbulence channel (saturated) are considered. Closed-form error rate expressions are derived using a series expansion of the modified Bessel function. Furthermore, the outage probability expressions are obtained for subcarrier intensity modulated optical wireless communication systems over the K-distributed turbulence and the negative exponential channels. Asymptotic error rate analysis and truncation error analysis are also presented. Our asymptotic analysis shows that differential phase-shift keying suffers a constant signal-to-noise ratio performance loss of 3.92 dB with respect to binary phase-shift keying under strong atmospheric turbulence conditions. The numerical results demonstrate that our series solutions are efficient and highly accurate.

Error Rate of Subcarrier Intensity Modulations for Wireless Optical Communications

Subcarrier intensity modulations are analyzed for the Gamma-Gamma turbulence channels. We study the error rate of a subcarrier intensity modulated wireless optical communication system employing phase-shift keying, differential phase-shift keying, and noncoherent frequency-shift keying. Closed-form error rate expressions are derived using a series expansion approach. Asymptotic error rate analysis and truncation error analysis are also presented. Our asymptotic analysis shows that the diversity order of the system and the signal-to-noise ratio penalty factors for noncoherent modulations depend only on the smaller channel parameter.