Multipath Rayleigh Fading Channels Research Articles

A high-data-rate hybrid index communication system based on quadrature chaos shift keying

To address the rapidly increasing challenges posed by the demands for large-scale data transmission and processing, this paper proposes a high-data-rate hybrid index modulation communication system based on quadrature chaos shift keying (HR-HIM-QCSK). The system employs a hybrid modulation involving carrier index and slot index. In this approach, three mutually orthogonal reference signals are constructed using Walsh codes. These reference signals are then utilized to create three distinct QCSK signals, distinguishing between the activation modes of carriers and time slots. This design allows all slots to carry QCSK signals, significantly enhancing the data rate of the HR-HIM-QCSK system. Theoretical analysis and simulations conducted under additive white Gaussian noise and multipath Rayleigh fading channels demonstrate that the HR-HIM-QCSK system outperforms other competing systems in terms of bit error rate (BER) performance. Further analysis covers aspects such as data rate, spectral efficiency, complexity and covertness, highlighting the superior performance of the HR-HIM-QCSK system in high-data-rate communication. This study provides valuable insights for the design of efficient chaotic communication systems.

Analysis of PLS enhancement using permutation index based OFDM-DCSK system over multipath Rayleigh fading channel

Analysis of PLS enhancement using permutation index based OFDM-DCSK system over multipath Rayleigh fading channel

Performance Analysis of Cooperative Spectrum Sensing using Empirical Mode Decomposition and Artificial Neural Network in Wireless Regional Area Network

Background: Radio spectrum is natural and the most precious means in wireless communication systems. Optimal spectrum utilization is a key concern for today's cutting-edge wireless communication networks. The impending problem of the lack of available spectrum has prompted the development of a new idea called “Cognitive Radio” (CR). Cooperative spectrum sensing (CSS) is utilized to improve the detection performance of the system. Several fusion algorithms of decision-making are proposed for sensing the licensed user, but they do not work well under low signal-to-noise ratio (SNR). Objectives: To address the issue of poor detection performance under low SNR, Empirical mode decomposition (EMD) and artificial neural network (ANN) based CSS under Rayleigh multipath fading channel in IEEE 802.22 wireless regional area network (WRAN) is proposed in this paper. Method: In this work, we propose the use of ANN as a fusion center. First, the received signal's energy is calculated using EMD. The computed energy, SNR, and false alarm probability are combined to form a data set of 2048 samples. They are utilized to train Levenberg- Marquardt back propagation training algorithm-based feed-forward neural network (FFNN). Using this trained network, CSS in WRAN is simulated under Rayleigh multipath fading. Results: Simulation results show that the proposed CSS method based on EMD-ANN outperforms the standard fast Fourier transform (FFT) and EMD detection-based cooperative spectrum sensing with a hard "OR" fusion at low SNR. With Pf =0.01, 100% detection accuracy with proposed techniques is obtained at SNR= -22dB. Conclusion:: The findings show that the suggested approach outperforms EMD and FFT based energy detection scheme-based traditional CSS in low SNR environments.

SLM based Circular (6, 2) mapping scheme with improved SER performance for PAPR reduction in OCDM without side information

Abstract Like OFDM, OCDM signal also suffers from high PAPR. SLM is an attractive PAPR reduction method but it needs to transmit the information regarding phase sequence i.e. SI to the receiver, which results in reduction in SE and data rate. Various SLM based SI free and SI embedding schemes are available in the literature. In this paper, different possible quaternary to 8-QAM mapping schemes for SI free SLM based PAPR reduction in OCDM system are discussed. Moreover, a new mapping scheme to eliminate the SI requirement has also been presented in this manuscript for SLM based PAPR reduction in OCDM system. Proposed Circular (6, 2) mapping scheme doesn’t require SI at the receiving end which results in increase in SE and data rate as compared to standard SLM technique. Random sequence with phase factors {1, −1} is used to generate the phase sequences for the proposed mapping scheme. Also, the analytical expression for SER of Circular (6, 2) mapping scheme over AWGN channel is derived. We have also evaluated the mathematical expression for SER of other possible quaternary to 8-QAM mapping schemes. Computer simulation using MATLAB are also carried out to investigate the performance of all these mapping schemes in terms of PAPR reduction performance as well as SER performance over AWGN and multipath Rayleigh fading channel. Proposed scheme achieves the same PAPR reduction and improved SER performance w.r.t. other six schemes taken into consideration.

Joint Grouping Subcarrier and Permutation Index Modulations Based Differential Chaos Shift Keying System

A joint grouping subcarrier-permutation index modulation based differential chaos shift keying (GSPIM-DCSK) communication system is proposed in this paper in order to enhance the energy and spectral efficiency, and increase the data rate of grouping subcarrier index modulation in DCSK (GSIM-DCSK) system that was recently suggested. In this system, the reference chaotic sequence is loaded into a permutation generator block to construct different permuted replicas of the reference sequence, and the input data bits for each symbol duration are divided equally into G parallel groups, each group consisting of carrier index bits indicated by p1 used for selecting active or inactive subcarrier out of2p1 subcarriers for GSPIM-DCSKI and GSPIM-DCSKII systems respectively, and permutation index bits,p2, that are used to select one chaotic sequence out of 2p2 permuted replicas of the reference chaotic sequence and then used this sequence to spread the modulated bit,p3=1, to send it through active subcarriers so the total number of transmitted bits for GSPIM-DCSKI and GSPIM-DCSKII systems is G (p1+p2+ 1) and G (p1+(2p1-1)(p2 +1)) respectively. The expressions for energy and spectral efficiency, as well as the complexity of the suggested schemes, are determined and compared the outcomes with other traditional DCSK schemes. Under the influence of additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels, the analytical expressions for BER of the two proposed systems are derived. The simulated and analytical BER results are compared to confirm the precision of BER analysis. Additionally, a comparison is made between the findings of the proposed schemes and those of traditional DCSK schemes, indicating that the suggested methods boost the performance of traditional DCSK schemes.

Design of Chaotic-Based PPM-PI-DCSK Modulation for Wireless Communications

In this letter, a joint pulse position modulation (PPM) and permutation index differential chaos shift keying (PI-DCSK) modulation scheme (PPM-PI-DCSK) is proposed to increase the data rate and improve performance. In PPM-PI-DCSK, the bit stream is divided into blocks of mp+mc+1 bits, where mp bits are modulated by PPM, mc bits are modulated by PI modulation, and the last one bit is modulated by DCSK. The theoretical bit error rate (BER) performance of the proposed PPM-PI-DCSK is derived over multipath Rayleigh fading channels and validated via simulations. Simulation results show that the proposed PPM-PI-DCSK outperforms the benchmark DCSK-based schemes. Furthermore, the performance superiority is also demonstrated by the frequency-modulated PPM-PI-DCSK over a typical ultra-wideband (UWB) channel. This demonstrates the superiority and feasibility of the proposed scheme in practical applications.

Performance of Broadcast Channel Using Hierarchical Modulation in OFDM Downlink

This paper proposes a multiple code block transmission scheme using hierarchical modulation (HM) for a broadcast channel in the orthogonal frequency division multiplexing downlink. We investigate the average bit error rate (BER) performance of two-layer HM using 16 quadrature amplitude modulation (QAM) and three-layer HM using 64QAM in multipath Rayleigh fading channels. In multiple code block transmission using HM, the basic information bits are demodulated and decoded to all users within a cell that satisfy the bit error rate (BER) requirement. Hence, we investigate non-uniform QAM constellations to find one that suppresses the loss in the average BER of the basic information bits for HM to a low level compared to that using the original constellation in which only the basic information bits are transmitted while simultaneously minimizing the loss in the average BER of the basic information bits for the secondary and tertiary information bits from the original constellations in which the information bits of the respective layers are transmitted alone. Based on the path loss equations in the Urban Macro and Rural Macro scenarios, we also investigate the maximum distance from a base station (BS) for the information bits of each layer to attain the required average received signal-to-noise power ratio that achieves the average BER of 10-3.

A New Receiver Design for Protograph-Coded Reference Reused DCSK Systems

In this letter, we investigate the performance of protograph-coded reference reused differential chaos shift keying (DCSK) systems to improve the transmission reliability. The traditional protograph-coded DCSK receiver does not take full advantage of the reused chaotic reference signals and hence cannot obtain desirable error performance. To solve this problem, we design a new receiver architecture called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">weighted reference estimation and iterative decoding (WRE-ID)</i> , which can universally improve the performance of protograph-coded reference reused DCSK systems over both multipath Rayleigh fading and additive white Gaussian noise channels. In particular, we put forward the WRE algorithm to estimate reference signal in order to calculate log-likelihood ratio (LLR) more precisely. Furthermore, extrinsic information output from the decoder is utilized to iteratively recalculate the weight of the WRE algorithm. As a further illustration, we derive the LLR expressions of the proposed WRE-ID-aided receiver of a typical protograph-coded reference reused DCSK (i.e., high-efficiency DCSK) system. Analytical and simulated results show that the proposed WRE-ID-aided receiver can always overtake the traditional receivers in reference reused DCSK systems. Hence, the protograph-based reference reused DCSK systems with the proposed receiver are very promising for high-rate high-reliability wireless applications.

Closed-Form Expressions of Upper Bound for Polarization-MDCSK System.

The performance analysis of polarization M-ary differential chaos shift keying (P-MDCSK) has been expressed using a tight upper bound with the Q-function. However, evaluating the Q-function directly is not a closed expression and there has been less work on closed expression for the upper bound. In order to solve the problem, this paper presents approximate closed-form expressions on the error probability of P-MDCSK. This expression is derived by employing a polynomial approximation of the Q-function. These closed-form expressions are verified through simulations conducted under both additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels. The simulation results reveal that there exists only a negligible gap between the simulations and the derived closed-form expressions. For example, it is observed that the theoretical approximate closed-form expressions exhibit a marginal deviation of approximately 0.4 dB from the simulations when the bit error rate (BER) reaches 10-4. Although the proposed method can only give approximate closed-form expressions of the upper bound, it provides an effective method for other communication schemes where the exact BER closed-form formula cannot be obtained.

Concentric triangular mapping with iterative substitution method for PAPR reduction in OCDM system without SI

Abstract OCDM, a new MCM scheme, has been proposed in the literature. Like widely used OFDM, OCDM also has a drawback of high PAPR. PAPR reduction schemes like SLM and PTS require information about phase factors i.e. SI used at the transmitting end for PAPR reduction for recovery of original data signal at the receiver. Transmission and recovery of SI is always a concern. In this paper a new CTM-IS method has been proposed for PAPR reduction of OCDM signal without SI. Main objective of the proposed scheme is to improve the error performance of SI free SLM and PTS based schemes without any degradation in PAPR reduction. PAPR performance and SER performance, over AWGN as well as multipath Rayleigh fading channels, of OCDM signal with proposed CTM-IS scheme is evaluated. Analytical expression for SER of the proposed CTM-IS scheme over AWGN channel is also derived. The computational complexity of the proposed CTM-IS scheme is also presented. Performance of the proposed CTM-IS scheme is compared with the existing MSM combined with SLM (MSM-SLM), CCM combined with SLM (CCM-SLM) and OM combined with SLM (OM-SLM) schemes. The proposed CTM-IS scheme has demonstrated to offer a theoretical power gain of about 3.01 dB, 2.55 dB, and 14.23 dB over MSM-SLM, CCM-SLM and OM-SLM schemes, respectively. Proposed CTM-IS scheme provides better SER performance with respect to MSM-SLM, CCM-SLM and OM-SLM without any loss in the PAPR performance. Moreover, computational complexity of CTM-IS scheme is less than that of MSM-SLM and CCM-SLM schemes.

PERFORMANCE IMPROVEMENT OF TWO-WAY COOPERATIVE DCSK SYSTEM USING GROUPING SUBCARRIER-PERMUTATION INDEX MODULATION

This paper proposes a new two-way half-duplex cooperative communication system based on a new chaotic modulation scheme called Joint Grouping Subcarrier-Permutation Index Modulation-based Differential Chaos Shift Keying (GSPIM-DCSK) in order to enhance its energy efficiency, data rate, and BER-performance. GSPIM-DCSKI utilizes a permutation index to load additional data bits, and the input bits are divided into groups that contain carrier, permutation, and modulated bits. The active and within each group are selected based on carrier index bits. The energy and spectral efficiency of the GSPIM-DCSKI systems are evaluated and compared to GSIM-DCSKI. The performance of the new schemes is evaluated by calculating the bit error rate (BER) under different channel conditions. Finally, the BER performance of the new cooperative system using GSPIM-DCSKI is compared to a traditional cooperative system using DCSK and proves that the new cooperative system has a better performance than the traditional one in different channels. Simulation results show that at the multipath Rayleigh fading channel the proposed cooperative system gained SNR about 3 dB at a BER level of 10^(-3) at than the traditional one and this gain is increased to equal 4 Db when p2=4.

MODELING OF A DIGITAL COMMUNICATION SYSTEM WITH INTERFERENCE-RESISTANT CODING OVER DELAYED MULTIPATH CHANNELS FOR A FIXED WIRELESS ACCESS SYSTEM

&#x0D; &#x0D; &#x0D; In this study, an analysis of the performance of a digital communication system was conducted to improve the efficiency of the communication channel. The system was de- signed and evaluated in the MatLab/Simulink environment, specifically for the transmission of binary data in a multipath channel with static fading. One of the main advantages of this system is its ability to provide high noise immunity, even in the presence of noise, interference, and signal delays. The performance of the system was investigated in terms of bit error rate (BER) over both an additive white Gaussian noise (AWGN) channel and a multipath Rayleigh fading channel. The study also considered the impact of inter-symbol interference (ISI) and explored different parameters for a static channel, resembling a wireless LAN system based on IEEE 802.11 (as defined by Rec ITU-R M.1225). This study uses a solution to suppress inter-symbol interference using cascading coding (convolutional turbo codes with Reed Solo- mon code), Fast Fourier Transform (FFT) and Inverse Fast Fourier Transform (IFFT), amplifiers at the transmitter side and normalizer at the receiver side, by regulating the amplification ratios of transmitter and receiver sides. Modeling of a digital communication system for a wide-band fixed wireless LAN system (for Indoor office and Outdoor to indoor systems) has been performed. The modeling outcomes show that the applied method provides a good per- formance improvement in channels with ISI with static fading.&#x0D; The application of cascading coding (turbo code together with RS code), amplifiers, and FFT on the transmitter side, and IFFT on the receiver side will eliminate the effects of inter-symbol interference on digital signals in a multipath channel with static fading (as defined by Rec. ITU-R M.1225 for internal and external transmission systems) for wireless fixed systems.&#x0D; &#x0D; &#x0D;

Design and Analysis of a New Index-Modulation-Aided DCSK System With Frequency-and-Time Resources

We propose a new index-modulation-aided differential chaos shift keying (DCSK) system using frequency-and-time resources, referred to as CTIM-DCSK system, to achieve high-data-rate transmissions. In the proposed system, the orthogonal sinusoidal carriers are used to transmit both the reference-chaotic and the information-bearing signals. Moreover, the frequency-and-time resources are considered as indices to carry additional information bits. To simultaneously boost the bit error rate (BER) performance and reduce the system complexity, this paper proposes a new CTIM-DCSK signal based on the frequency-and-time resources, in which the time slots used by the selected subcarriers convey the same index bits. We employ a noise-reduction method at the receiver to further improve the BER performance of the proposed CTIM-DCSK system. We also derive the theoretical BER expressions of the CTIM-DCSK system over two different channels, i.e., additive white Gaussian noise (AWGN) channel and multipath Rayleigh fading channel. We analyze the data rate, complexity and spectral efficiency of the CTIM-DCSK system in comparison with the state-of-the-art counterparts. Analytical and simulation results verify the accuracy of the theoretical analysis and the advantage of the proposed CTIM-DCSK system. Consequently, the proposed CTIM-DCSK system appears to be a competitive candidate for low-complexity Internet-of-Things applications.

Design of a Differential Chaotic on-off keying communication system

Among the available chaotic modulation schemes, differential chaos shift keying (DSCK) offers the perfect noise performance. The power consumption of DCSK is high since it sends chaotic signal in both of 1 and 0 transmission, so it does not represent the optimal choice for some applications like indoor wireless sensing where power consumption is a critical issue. In this paper a novel noncoherent chaotic communication scheme called differential chaos on-off keying (DCOOK) is proposed as a solution of this problem. With the proposed scheme, the DCOOK signal have a structure similar to chaos on-off keying (COOK) scheme with improved performance in noisy and multipath channels by introducing the concept of differential coherency used in DCSK. The simulation results show that the proposed scheme have achieved more than 3 dB gain in signal-to-noise ratio for AWGN and Rayleigh multipath fading channels at BER=10-3 over COOK scheme.

Design of a Reconfigurable Intelligent Surface- Assisted FM-DCSK-SWIPT Scheme With Non-Linear Energy Harvesting Model

In this paper, we propose a reconfigurable intelligent surface (RIS)-assisted frequency-modulated (FM) differential chaos shift keying (DCSK) scheme with simultaneous wireless information and power transfer (SWIPT), called RIS-FM-DCSK-SWIPT scheme, for low-power, low-cost, and high-reliability wireless communication networks. In particular, the proposed scheme is developed under a non-linear energy-harvesting (EH) model which can accurately characterize the practical situation. The proposed RIS-FM-DCSK-SWIPT scheme has an appealing feature that it does not require channel state information, thus avoiding the complex channel estimation. We further derive the closed-form theoretical expressions for the energy shortage probability and bit error rate (BER) of the proposed scheme over the multipath Rayleigh fading channel. In addition, we investigate the influence of key parameters on the performance of the proposed transmission scheme in two different scenarios, i.e., RIS-assisted access point (RIS-AP) and dual-hop communication (RIS-DH). Finally, we carry out various Monte-Carlo experiments to verify the accuracy of the theoretical derivation, illustrate the performance advantage of the proposed scheme, and give some design insights for future study.

DPI DCSK Modulation with BCJR Decoding

This paper proposes a novel [Formula: see text]-ary differential permutation index (DPI) differential chaos shift keying (DCSK) by using the Bahl–Cocke–Jeline–Raviv (BCJR) decoding (DPI-DCSK-BCJR) for chaos-based communications. By exploiting the characteristics of differential modulation and quasi-orthogonality of chaotic signals, the proposed DPI-DCSK-BCJR can provide two more calculated energies to decide the transmitted bits. Theoretical analysis of bit-error-rate (BER) is carried out over multipath Rayleigh fading channel and then validated via simulations. The proposed scheme is demonstrated to outperform the conventional DPI-DCSK by 2[Formula: see text]dB for different [Formula: see text]. This performance gain is especially increased over high-delay channels. Furthermore, the advantage of the proposed frequency-modulated DPI-DCSK-BCJR is verified over practical ultra-wideband (UWB) wireless channels. In addition, we investigate the proposed DPI-DCSK-BCJR for more generalized multiuser communications. The simulation result shows that DPI-DCSK-BCJR can achieve performance gains up to 5[Formula: see text]dB as compared to the conventional PI-DCSK and DPI-DCSK for both two and three user systems. Consequently, the proposed DPI-DCSK-BCJR can be considered as a low-cost alternative for low-complexity and high-rate chaotic-based wireless communication.

A Novel Coupled Code Shifted M-ary Differential Chaos Shift Keying Modulation

In this paper, a novel coupled code shifted M-ary differential chaos shift keying modulation scheme is proposed as a simple and low-cost solution to reference removal. In this scheme, only two information-bearing signals are transmitted. Both signals are modulated by selected Walsh code sequences with specific indices determined by the index bits, and one of them also carries an additional M-ary information symbol. Since these two information-bearing signals are coupled by the same chaotic message bearer, data bits can be easily recovered according to the correlation between these two signals so that the transmission of reference signals can be completely avoided. Theoretical Bit Error Rate (BER) expressions are derived over the additive white Gaussian noise and multipath Rayleigh fading channels. Furthermore, simulations and comparisons indicate that the proposed system can achieve better BER performance with lower complexity.

Design and Performance Analysis of RIS-Aided DCSK-WPC System With Energy Buffer

This paper proposes an energy buffer and reconfigurable intelligent surface (RIS) aided differential chaos-shift-keying (DCSK) wireless-powered communication (WPC) system, which includes an access point (AP), a RIS, and a source node equipped with an energy buffer. In such system, the source node first harvests and stores radio-frequency energy from the AP in the downlink, then uses the stored energy to transmit information to the AP in the uplink. A simple time-switching scheme for the proposed system is designed. Two different energy management policies at the source node are considered, i.e., best-effort policy (BEP) and on-off policy (OOP). The bit-error-rate (BER) expressions of the proposed system with BEP and OOP are derived over multipath Rayleigh fading channels. Results demonstrate that the proposed system is able to achieve better BER performance than the conventional DCSK-WPC system and the RIS aided DCSK-WPC buffer-less system, while keeping the non-coherent feature of the DCSK system.

A Novel Differential Chaos Shift Keying Scheme With Multidimensional Index Modulation

A new differential chaos shift keying scheme with multidimensional index modulation, referred to as MIM-DCSK scheme, is proposed in this paper. This design objective of the proposed MIM-DCSK scheme is to enhance the data rate, energy efficiency, and spectral efficiency of traditional DCSK scheme. In the proposed MIM-DCSK scheme, in addition to the information bits allocated for physical transmission, multidimensional transmission entities, namely the time slot, carrier, and Walsh code are simultaneously considered as indices to convey additional information bits, thus achieving high data rate, spectral efficiency, and energy efficiency. The theoretical bit-error-rate (BER) expressions of the MIM-DCSK scheme are derived over additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels. Furthermore, the data rate, complexity, spectral efficiency, and energy efficiency of the MIM-DCSK scheme are analyzed. Simulation results verify the accuracy of the theoretical analysis and illustrate the superiority of the proposed scheme. The proposed MIM-DCSK scheme is a promising solution for low-power and low-cost short-wireless communications.

Design of a New Non-Coherent Cross-QAM-Based M-ary DCSK Communication System

In this paper, a new non-coherent cross-quadrature amplitude modulation (XQAM)-based M-ary differential chaos shift keying (XQAM-MDCSK) system is proposed. In such a system, an autocorrelator is adopted at the receiver to obtain the channel compensation value. This framework can be extended to various amplitude phase shift keying-based MDCSK systems, such as star QAM-based MDCSK (star QAM-MDCSK) and square QAM-based MDCSK (SQAM-MDCSK) systems. Moreover, the bit error rate (BER) expression of the proposed XQAM-MDCSK system is derived over a multipath Rayleigh fading channel. Results show that the proposed XQAM-MDCSK system can achieve better BER performance and a lower peak-to-average power ratio (PAPR) compared to the star QAM-MDCSK system. Furthermore, we also show that the performance of the proposed system can be close to that of a system with perfect channel state information (CSI).