Reduce Intersymbol Interference Research Articles

Comparative study of 2FSK and GFSK modulation and demodulation techniques

In the digital communication era, efficient data transmission is paramount, spanning applications from mobile communication to satellite systems. Digital modulation, the process of converting digital data into a suitable format for transmission, plays a pivotal role in ensuring reliability and efficiency. This paper delves into the world of digital modulation, specifically focusing on Frequency Shift Keying (FSK) techniques. FSK encodes digital information using different carrier frequencies, making it adaptable and robust, particularly in noisy channels. This paper explores two variants: 2-level Frequency Shift Keying (2FSK) and Gaussian Frequency Shift Keying (GFSK). 2FSKs simplicity and noise tolerance make it ideal for applications like wireless LANs and radio broadcasting. However, it may not be the best choice for high-data-rate applications due to limited bandwidth efficiency. GFSK employs Gaussian filtering to reduce spectral width, enhancing bandwidth efficiency and reducing inter-symbol interference. It finds extensive use in applications like Bluetooth. This paper explores the modulation and demodulation processes for both techniques, emphasizing GFSKs spectral efficiency. Future trends encompass emerging technologies like signal processing and machine learning, reshaping telecommunications and IoT. In conclusion, understanding 2FSK and GFSK modulations nuances aids engineers and researchers. Future endeavors should focus on optimizing GFSKs bandwidth efficiency and bolstering demodulation techniques.

OPTIMAL DETECTION OF SIGNALS SEQUENTIALLY MODULATED BY PSEUDO NOISE IN RADAR FOR RESCUERS

Searching for living people under the rubble of buildings collapsed due to man-made or natural disasters, special radars play an important role, which allow you to see a living person behind optically opaque obstacles. The information sign of a living person in the reflected signal is the Doppler modulation of the signal phase, due to the processes of breathing and heartbeats. This phase modulation has an ultralow frequency and can be effectively detected using long pseudo-noise probing signals, for example, based on Mersenne codes. To reduce inter-symbol interference in the code sequence, a linear correlation receiver is built. Its signal processing algorithm is based on all received patterns observed during a fixed interval. The decision in favor of the first character in the chosen code combination is made under the assumption of ideal feedback, which provides almost the maximum error probability characteristics in systems with a serial Mersenne code.

A machine learning-based concentration-encoded molecular communication system

Molecular communication (MC) is a recent novel communication paradigm, which could enable revolutionary applications in the fields of medicine, military, and environment. Inspired by nature, MC uses molecules as information carriers to transmit and receive data. Concentration-encoded molecular communication (CEMC) is an information encoding approach, where the information is encoded in the concentration of the transmitted molecules. In this paper, we propose a machine learning (ML)-based CEMC system. In particular, we propose a modulation scheme named concentration position-shift keying (CPSK), which encodes information as the position of the transmitted molecular concentration. After passing through a diffusion-based channel, the molecules are captured via a ligand–receptor binding process (LRBP) at the nanoreceiver. Then, a ML-based approach is employed to decode the data bits. From numerical simulations, it has been shown that increasing the transmission time and using 4-ary CPSK would enhance the communication performance of the proposed ML-based CEMC system. In addition, we found that the ML receiver mitigates the bias effect and reduces inter-symbol interference (ISI) of the diffusion-based molecular channel. As a result, the proposed ML-based receiver shows better performance than the conventional maximum-likelihood (MLE) receiver.

Adaptive Blind MPSK Constellation Recovery and Equalization for Cognitive Radio Applications

Cognitive radio is considered a relevant communication paradigm to deal with the increasing demands in modern communications systems. Adaptive schemes are required to recognize channel conditions and to properly adjust main transmission parameters to improve the quality of communications. In this direction, blind algorithms to recover constellation, from phase-modulated signals, represent a means to implement cognitive capabilities to allow automatic modulation recognition (AMR) on receivers. Commonly, the most popular approaches for blind constellation recovery are based on a two-step scheme. The first step uses to equalize channel effects and reduce inter-symbol interference (ISI). The second step carries out constellation recovery utilizing phase locked loop (PLL) systems like the Costas Loop, then to classify the incoming signal. This work proposes a novel single-step blind adaptive filter solution, inspired by an adaptive interference canceler, for joint equalization and constellation symbol recovery from received phase shift keying (PSK) waveforms. Furthermore, we propose new coefficients update mechanisms based on the constant amplitude of PSK signals. The proposed solution exhibits reduced computational complexity compared to the state of the art and a reduced time of convergence. Additionally, the proposed scheme does not require a training sequence to operate properly. The obtained results clearly show that the proposed scheme significantly improves accuracy regarding phase symbol estimation and ISI reduction.

Performance Improvement of DS-CDMA IVC by Reducing Intersymbol Interference in Urban Environment

Performance Improvement of DS-CDMA IVC by Reducing Intersymbol Interference in Urban Environment

A novel spread spectrum underwater acoustic communication system for the inter-symbol interference reduction

A novel spread spectrum underwater acoustic communication system for the inter-symbol interference reduction

A novel spread spectrum underwater acoustic communication system for the inter-symbol interference reduction

A novel spread spectrum underwater acoustic communication system for the inter-symbol interference reduction

Multilevel Redundant Discrete Wavelet Transform (ML-RDWT) and Optimal Red Deer Algorithm (ORDA) Centred Approach to Mitigate the Effect of ICI, BER and CIR in a MIMO-OFDM System

Nowadays, there is a great demand for ultra-high data rate (UHDR) transmission on most 5th generation wireless networks. In this concern, the multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) scheme is used on a large scale to achieve UHDR transmission with reduced inter-symbol interference (ISI) and inter-carrier interference (ICI). Discrete wavelet transform-based OFDM (DWT-OFDM) provides better orthogonality due to presence of orthogonal wavelets, which mitigates the effects caused by ISI and ICI. Also, it has extended bandwidth than the traditional OFDM systems. But a major drawback in this system is that it suffers from down sampling. The down-sampling effect reduces the actual size of the input bit streams. As a result, the system performance is degraded. For solving this problem, a multilevel redundant discrete wavelet transform (ML-RDWT) is used instead of DWT to achieve improved spectral performance. Here, complex down-sampling operation is eliminated. From the simulation outcomes, it is clearly viewed that effects caused by ICI, ISI and BER are mitigated by improving the performance of CIR. The proposed method employs optimal red deer algorithm (ORDA) to locate the optimized weights for the ICI cancellation system. This algorithm enhances the spectral efficiency by achieving high CIR with reduced BER, ISI and ICI. The BER in the proposed MIMO-ML-RDWT-OFDM-ORDA method is 68%, 76%, 38% and 75%, which is very low when compared to the BER in the existing techniques like MIMO-DWT-OFDM-RDA, MIMO-RNS-OFDM-PNMA, MIMO-OFDM-BMA and MIMO-OFDM-ICIMA. The ISI in the proposed method is 94%, 91%, 95% low when compared to the ISI in the existing techniques. The ICI in the proposed work is 71%, 57%, 73% and 86% low when compared to the ICI in the existing techniques. Therefore, the general performance of the proposed MIMO-ML-RDWT-OFDM-ORDA method is improved in an efficient way with less complexity, error rate and processing delay.

A Performance Analysis of Wavelet based LTE-OFDM with Multi-equalizers

A rapid change in usage of mobile data and mobile based applications such as online gaming, mobile TV etc. motivates the mobile wireless communication system to work on new emerging trends Long Term Evolution (LTE). LTE-4G architecture provides an optimized packet based radio access technology. The basic signal format of LTE is Orthogonal Frequency Division Multiplexing (OFDM) Modulation. This modulation scheme satisfies the spectrum flexibility requirement in LTE. LTE-MIMO-OFDM with IFFT and FFT transform introduced to provide the cost-effective solution for very wide carriers with high PAPR. Inter-symbol Interference (ISI) and inter carrier interference (ICI) are predominant factors which exist in the wireless communication channel. Existing methods of ISI and ICI reduction to improve signal quality have been achieved using conventional OFDM techniques. However, a better modulation scheme is required to achieve high data rate, low latency and flexible bandwidth deployment. This paper has proposed a Wavelet based LTE-MIMO-OFDM modulation scheme with multi equalizer that improves the performance of system by reducing PAPR and BER in MCM. Experimental results show the performance of this scheme and the results is compared with existing MMSE and Multi equalizer MMSE and achieves a flexible spectral efficiency with reduction of PAPR and BER.

A Parallel Transmission Scheme Based on the Turbo Product Code for Through Silicon via Array in Three-Dimensional Integrated Circuits

Through silicon via (TSV) is the key technology for the vertical interconnect in three-dimensional integrated circuits (3-D ICs). With the help of TSVs, higher throughput in signal transmission can be attained. However, the tightly clustered TSVs in the TSV array suffer from crosstalk noise, a situation which results in transmission errors. This study investigates, the channel model of the TSV array, involving main factors affecting transmission performance, such as transmission loss, inter-channel interference, and crosstalk noise with different digital patterns. A parallel transmission scheme based on a turbo product code (TPC) parallel coding is proposed. In this scheme, the binary bits of information are reshaped into two dimensional blocks. Each block is parallel encoded using a TPC into a codeword block for parallel transmission through the TSV array channel. At the receiver, the sending information is reformed by a concurrent hard decision decoding algorithm of a TPC. This parallel transmission scheme achieves low bit-error-rate, high throughput, and a lower system overhead relative to that of its ground TSV shielded counterpart if the type of TPC is carefully selected. The simulation results confirm that this scheme reduces inter-symbol interference, minimizes structural defects in the TSV array, and improves transmission performance in 3-D ICs.

Mitigating interference and reducing detection complexity in asynchronous cooperative relay network utilising new distributed space time block coding

The synchronisation in wireless cooperative relay networks is impossible to achieve in real environment utilising orthogonal space time block coding. There have been several approaches proposed to mitigate the effect of synchronisation among the relay nodes at the receiver. All have managed to reduce the inter-symbol interference at the expense of low data rate with high detection complexity. Others achieved full data rate and high cooperative diversity using high decoding complexity that requires a feedback link. In this paper, a new approach is presented that reduces inter-symbol interference, achieves full data rate and full cooperative diversity with low complexity. This uses a new efficient distributed orthogonal space time block coding design with a sub-optimum detection scheme utilising dual relay nodes. This reduces the number of timing misalignments among the relay nodes and minimises the detection complexity. Furthermore, the new proposed method uses linear decoding process to achieve full data rate and full cooperative diversity without the need for any a feedback link. The analytical analysis and simulation results confirmed that sub-optimum approach with the new efficient design are very effective at reducing the lack of synchronisation among the relay nodes at the destination node with low encoding and decoding complexities.

Transmission of Images on High-Temperature Nuclear-Grade Metallic Pipe with Ultrasonic Elastic Waves

Transmission of information using elastic ultrasonic waves on existing metallic pipes provides an alternative communication option for a nuclear facility. The advantages of this approach consist of transmitting information through barriers, such as the containment building wall, with minimal modification of the existing hardware. Because bit rates on the order of kilobits per second are achievable, relatively large volumes of data, such as images, can be transmitted. A viable candidate for an ultrasonic communication channel is a stainless steel pipe of the chemical volume control system (CVCS) that penetrates through the reactor containment building wall through a sealed tunnel. To study ultrasonic communication under simulated nuclear facility conditions of high temperature, a test article was developed by installing heating tapes, temperature controllers, and thermal insulation on a laboratory CVCS-like stainless steel pipe. High temperature and radiation-resilient lithium niobate ultrasonic transducers were utilized for information transmission on the heated pipe. The amplitude shift keying (ASK) digital communication protocol was developed and implemented in a GNU Radio software–defined radio environment. A root-raised-cosine filter was introduced to suppress ultrasonic transducer ringing and thus reduce inter-symbol interference. This resulted in the enhancement of the data transmission bit rate compared to information encoding with square pulses. Demonstrations of communication at high temperature included transmission of a 90-KB image at the bit rate of 10 Kbps with a bit error rate of 10−3 across a 6-ft-long straight pipe heated up to 230°C. Additional preliminary studies were conducted to evaluate ultrasonic communication system resilience to environmental degradation and damage.

Reduction of Intersymbol Interference in DS-CDMA IVC Based on Location-Oriented Code Allocation

Reduction of Intersymbol Interference in DS-CDMA IVC Based on Location-Oriented Code Allocation

Multiplexed terrestrial free space optic system design using dual polarized multicarrier transmission technique

A hybrid technique for terrestrial free space optic (FSO) system has been proposed in this paper. The hybrid technique is a combination of 8 × 40 Gbps dense wavelength-division multiplexing and a multicarrier transmission (MCT) scheme such as coherent optical orthogonal frequency-division multiplexing (CO-OFDM). The prime design objective is to minimize the issues related to the terrestrial FSO-based system for atmospheric turbulence, bandwidth management, and receiver sensitivity. The cyclic prefix bits have been added with the data symbols of CO-OFDM, which minimizes the effect of nonlinearity due to atmosphere and reduces intersymbol interference. The dual-polarized quadrature phase-shift keying (DP-QPSK) sequence is used to modulate the subcarriers of the MCT system. DP-QPSK is very well known for its optical signal-to-noise ratio tolerance. It has been found that, by the incorporation of a hybrid scheme in the FSO system, a propagation range of 2.2 km in atmospheric turbulence regime for the targeted bit error rate (BER) of 3.8 × 10 − 3 or log of BER of −2.42 is achieved. A contrast performance comparison has also been carried out for the proposed hybrid system with different advanced modulation schemes such as differential quaternary phase-shift keying and four-level quadrature amplitude modulation. The Gamma-Gamma-type distribution function is considered for estimating the turbulence effect of the free space channel. Mathematical modeling related to the proposed system has also been incorporated for better analysis. This type of hybrid technique for the FSO system with the incorporation of DP-QPSK modulation format will give more technical feasibility to the modern communication system.

Analysis of Underwater Acoustic Communication System Using Equalization Technique for ISI Reduction

Underwater Acoustic Communication (UWAC) has been an active research area over a decade. Apart from regular communication inside the water, the applications include Remotely Operated Vehicles (ROV), Underwater Sensor Networks (UWSN), military and navigation applications, diving purposes, Autonomous Underwater Vehicles (AUV), underwater sports, etc. The major disadvantages of UWAC are frequency-dependent attenuation, short range of communication, very low bandwidth. In this paper, Modulation techniques such as BPSK, QPSK, and 4-QAM are used in UWAC in order to reach longer distances inside water. The fundamental key aspect of UWAC including significant multipath interference and strong ambient noise, are addressed. Equalization techniques are used at the receiver to overcome the Inter symbol Interference (ISI) caused due to multipath propagation. Zero Forcing (ZF) and Minimum Mean Square Error (MMSE) equalizers are used in this paper. However, ZF comes at the cost of increasing the noise; however; MMSE reduces all the noise levels in UWAC.

PAPR and ISI Reduction in Cognitive Radio Network based 5G Network using Massive MIMO SC - FDMA ES.

Extended use of spectrum increased the number of users; this was the major cause to introduce Cognitive Radio Networks (CRN) which is designed to access the available spectrum effectively. Advanced telecommunication technology that is fifth-generation (5G) is inbuilt in CRNs. Fusion Center (FC) in CRN plays an important role in decision making for allocating available spectrum. A novel FC rotation (FCR) method is applied over FC to mitigate the occurrence of interference. Massive-Multiple Input Multiple Output (MaMi) system is used to enhance network performances to accommodate the huge participation of users by means of having a large number of antennas. Existing research works in CRN based 5G network fails to decrease intersymbol interference (ISI) and Peak-to-Average Power Ratio (PAPR). A novel Massive MIMO SC – FDMA ES is proposed in this paper to mitigate high PAPR values to enhance network performance. Our proposed work in CRN is experimentally designed using Network Simulator 3 from which the performances are evaluated. The extensive simulation result shows betterment in terms of channel capacity, reduction of PAPR, bit error rate and spectral efficiency.

Doubly Orthogonal Wavelet Packets for Multi-Users Indoor Visible Light Communication Systems

Visible Light Communication (VLC) is a data communication technology that modulates the intensity of the light to transmit the information mostly by means of Light Emitting Diodes (LEDs). The data rate is mainly throttled by the limited bandwidth of the LEDs. To combat, Multi-carrier Code Division Multiple Access (MC-CDMA) is a favorable technique for achieving higher data rates along with reduced Inter-Symbol Interference (ISI) and easy access to multi-users at the cost of slightly reduced compromised spectral efficiency and Multiple Access Interference (MAI). In this article, a multi-user VLC system is designed using a Discrete Wavelet Transform (DWT) that eradicates the use of cyclic prefix due to the good orthogonality and time-frequency localization properties of wavelets. Moreover, the design also comprises suitable signature codes, which are generated by employing double orthogonality depending upon Walsh codes and Wavelet Packets. The proposed multi-user system is simulated in MATLAB software and its overall performance is assessed using line-of-sight (LoS) and non-line-of-sight (NLoS) configurations. Furthermore, two sub-optimum multi-users detection schemes such as zero forcing (ZF) and minimum-mean-square-error (MMSE) are also used at the receiver. The simulated results illustrate that the doubly orthogonal signature waveform-based DWT-MC-CDMA with MMSE detection scheme outperforms the Walsh code-based multi-user system.

A Survey on Optimization Based Spectrum Sensing Techniques to Reduce ISI and PAPR in OFDM Based Cognitive Radio System

Cognitive radio is emerging technologies in OFDM based wireless systems which are very important for spectrum sensing. By using cognitive radio (CR) high data can be transferred with low bit error rate. The key idea of OFDM is to split the total transmission bandwidth into the subcarriers which further reduce the intersymbol interference (ISI) and peak to average power ratio(PAPR) in the signal. There are many optimization based spectrum sensing techniques are existing for efficient sensing purpose but each has its own advantages and disadvantages. This leads to start the comprehensive study for reducing PAPR and ISI(Intersymbol interference) in terms of FPGA based partial configuration. In the first part of review OFDM characteristics of the signal has compared with several optimizations based ISI reduction techniques. The second part is to compare the various spectrum sensing techniques in cognitive radio engine and its application in FPGA.

A Survey on Optimization Based Spectrum Sensing Techniques to Reduce ISI and PAPR In OFDM Based Cognitive Radio System

Cognitive radio is emerging technologies in OFDM based wireless systems which are very important for spectrum sensing. By using cognitive radio (CR) high data can be transferred with low bit error rate. The key idea of OFDM is to split the total transmission bandwidth into the subcarriers which further reduce the intersymbol interference (ISI) and peak to average power ratio(PAPR) in the signal. There are many optimization based spectrum sensing techniques are existing for efficient sensing purpose but each has its own advantages and disadvantages. This leads to start the comprehensive study for reducing PAPR and ISI(Intersymbol interference) in terms of FPGA based partial configuration. In the first part of review OFDM characteristics of the signal has compared with several optimizations based ISI reduction techniques. The second part is to compare the various spectrum sensing techniques in cognitive radio engine and its application in FPGA

Inter-symbol interference reduction channel codes based on time gap in diffusion-based molecular communications

In diffusion-based molecular communication simple modulation techniques based on the concentration, type, or released time of molecules are commonly used. However, random delay of the diffused molecules in environment can cause some strong inter-symbol interference (ISI) among consecutive symbols. Due to the limited computational capabilities of nano-machines, sophisticated modulation and coding schemes cannot be used to resolve this issue . In this paper, we propose several new, yet simple, ISI-resistant coding schemes for diffusion-based communications over a one-dimensional noiseless channel. These schemes map the information bits into variable length codewords and place time-gaps between the consecutive codewords to mitigate ISI issue. Our analytical and simulation results indicate that the proposed schemes provide superior performances in terms of probability of error and throughput compared to the existing schemes.