Multi-frequency encoding technique using phase coupling in wireless communication systems

The direct sequence (DS) spread spectrum communication technique is widely regarded as one of the most effective methods of mitigating the effects of a repeating jammer in military communications systems. The proposed system coupled DS with multiple frequency shift keying (DS/MFSK). It is comprised of a transmitter and a receiver. Non-coherent demodulation is examined, as are the spreading sequences in question. The effect of AWGN and Rayleigh fading channels on the proposed approach's bit error rate (BER) is examined. The investigation demonstrates that even with an 8 dB signal-to-noise ratio, superior outcomes can be achieved; this study's suggested endeavor is to create a novel transceiver system built on the DS/MFSK modular architecture. MFSK modulation prevents multiple-access interference, while DS is typically employed to boost system efficiency across erratic fading. Test results show that reliability on the AWGN channel decreases a little while reliability is greatly enhanced by Rayleigh fading. Moreover, notable improvements in bandwidth efficiency are achieved.

Cardiac Ischemia (CI) is the most common type of cardiac arrhythmia. CI is caused by narrowing of arteries which makes less oxygenated blood to reach the heart muscle. This condition may lead to heart attack with no prior warning. This paper introduces the work that has been done to distinguish the Electrocardiogram (ECG) of a normal healthy person from that of CI patient. Normal spectral analysis of ECG provides only the power within frequency components but doesn't give any phase relations. Bispectral analysis - Bispectrum, Bicoherence and Quadratic Phase Coupling techniques are used to detect and characterize phase coupled harmonics in ECG. Normal Sinus Rhythm Data is obtained from MIT-BIH Database. CI data is obtained from European ST-T Database. The algorithm was tested on MIT-BIH database and European ST-T Database. This concept can be utilized to identify other heart diseases also.

We present the results of bicoherence analysis on observations of GRS 1915+105 that exhibit quasi-periodic oscillations (QPOs). The bicoherence is a higher order statistic that can be used to probe the relation between the phases of a triplet of Fourier frequencies. Despite showing very similar power spectra, the observations exhibit different patterns in their bicoherence, indicating that the QPOs are phase coupled to the noise in different ways. We show that the bicoherence pattern exhibited correlates with the frequency of the QPO, the hardness ratio, as well as the radio properties of the source. In particular, we find that the nature of phase coupling between the QPO and the high and low frequency broad-band components is different between radio quiet, radio plateau, and radio steep conditions. We also investigate the phase lag behaviour of observations with QPO frequency above 2 Hz that show different bicoherence patterns and find statistically significant differences between them, indicating a change in the underlying physical mechanism. Finally, we present a scenario whereby the cooling of the jet electrons by soft photons from the accretion disc could explain the observed correlations between the bicoherence and radio properties.

Direct sequence code division multiple access (DS-CDMA) and M-ary frequency shift keying (MFSK) are two viable modulation schemes for broadband power line communication (PLC) channels, for multi-carrier and single carrier cases respectively. In this paper, we study the bit error rate (BER) performance of a synchronous DS-CDMA system and an MFSK system employing coherent detection for a PLC channel. The background noise present in PLC channel is assumed to follow Nakagami-m distribution as suggested by earlier works. Thereafter a comparison is drawn between the two modulation schemes. In order to draw the comparison at an equal level, we analyse the BER performances of the two systems having the same degree of transmitter/ receiver complexity along with the criteria of same bandwidth occupation, same transmission power as well as the same PLC channel characteristics. The study provides an insight as to how a small change in the parameter of a random variable (RV) describing the background power line noise has a marked influence on the BER performances of the two modulation schemes mentioned above. Also from the simulation results obtained it is quite evident that for a single user case, the MFSK system outperforms the DS-CDMA system at similar data rates.

Background/Objectives: Tremendous growth in the mobile communication services in this technology driven era has made possible for the people to exchange information (data, voice or image) with each other while they are on the move. These wireless systems have brought a revolution in the current market for their high data rates and performance enhanced features. Methods/Statistical Analysis: One of the key issues affecting the performance of a wireless channel is the random variations in the signal strength which may be resulted due to some obstructions like buildings, trees, etc. or due to the movement of the mobile user. This leads to stochastic behavior of the radio channel.. A highly faded Two-Wave with Diffuse Power (TWDP) environment is discussed along with hybrid diversity combining technique. The effectiveness of this scheme is further evaluated by analyzing the system performance in terms of Bit Error Rate (BER) vs Signal to Noise Ratio (SNR). Binary Phase Shift Keying (BPSK) and Quadrature Phase Shift Keying (QPSK) modulation techniques were employed. Findings: It has been shown clearly that TWDP forms the poorer link when compared with other fading channels as BER is higher in this case. Moreover, TWDP fading environment can serve as the worst case scenario in wireless communication system. Also it has been shown as the diversity order increases system’s performance is improved in terms of BER and reduction in SNR requirement to achieve a constant BER value. Application/Improvement: This paper presents the need to obtain a clear perception of channel characteristics and to model a system for combating fading and improving the system performance by considering a TWDP fading channel instead of Rayleigh channel while designing a wireless communication system in worst channel conditions..

Orthogonal frequency division multiplexing (OFDM) is a type of digital modulation technique which is used in wireless communication systems. It is an efficient multicarrier modulation technique, in which large bandwidth is divided into parallel narrow bands each of which is modulated by different subcarriers. All the subcarriers are orthogonal to each other and hence it reduces the interference among various subcarriers. But OFDM suffers from high peak to average power ratio(PAPR), high complexity in design. The performance parameter of OFDM can be measured in terms of Bit error rate (BER). Lower the BER value, higher is the efficiency of OFDM system. Various methods are used to enhance the BER performance. Channel coding is the one way of enhancing the BER. This paper discusses the performance of OFDM using linear & cyclic block coding for different digital modulation techniques. Bit error rate (BER) is used to measure the performance of OFDM systems.

Relevance. In long-haul decameter-band (LDB) communication systems, the number of bit errors is simultaneously influenced by two key factors: the signal-to-noise ratio and the degree of phase distortions caused by the Doppler shift, which arises from the random movement of ionospheric inhomogeneities. The challenge of improving the interference resistance of such systems is complicated by the fact that even with a high signal level at the demodulator's input, reception can be hindered by phase distortions, leading to a sharp increase in the number of bit errors and a degradation of the BER (bit error rate) coefficient. Despite the sufficient number of classical works, the problem of enhancing the interference resistance of modern domestic LDB radio communication systems under specified operating scenarios using contemporary methods and digital signal processing tools remains relevant and in demandich lead to a sharp increase in the number of bit errors and a deterioration in the BER coefficient. Despite a sufficient number of classical works, the problem of improving the noise immunity of modern domestic LDB or short-wave (HF) radio communication systems in specified operating scenarios using modern methods and means of digital signal processing (DSP) remains relevant and in demand. The object of the research is modern domestic decameter-band radio communication systems, which often exhibit known shortcomings, including low adaptability to changes in the ionosphere and issues with signal interference. For example, the R-016 system has limitations in its frequency range, making it less effective under varying ionospheric conditions that affect signal levels. Prototypes may also have problems with signal processing, which leads to bit errors of up to 10-3 even in the absence of noticeable interference. The subject of the study is the models and methods of functioning of LDB decameter-band communication lines.The objective of the research is to evaluate the impact of various factors, such as changes in preamble length and the use of adaptive filters, on the interference resistance of the system. The analysis of the obtained results shows that increasing the preamble length in such systems contributes to enhancing the interference resistance of long-haul communication. The scientific novelty lies in the improvement of existing radio propagation models in the decameter range by applying a complex of parameters that includes the signal-to-noise ratio set for a specific communication session in the radio line, and to increase the accuracy of field strength calculations at the receiving point, recalculated values of critical frequencies based on electron concentration forecasts, as well as Doppler shift for each layer of the ionosphere. The practical significance of the results lies in the enhancement of the interference resistance of existing decameter-band communication systems in ionospheric propagation conditions.

Wireless communication with multicarrier modulation is very attractive for present and future communication network due to immunity to delay spread and fading. However, such systems are receptive to carrier frequency offset (CFO) due to Doppler effect in a mobile communication system. Analysis is carried out for a wireless communication system with multi carrier (MC) direct sequence (DS) code division multiple access (CDMA) technique with CFO to find the expression of SINR and the bit error rate (BER) with BPSK coherent detection receiver. The results are checked out in term of SINR and BER for various values of CFO variance, considering Gaussian distribution of CFO. The result shows that there occurs BER floor due to CFO for SC and Multi Carrier (MC) DS-CDMA and there is a power penalty at a given BER which is high for the Multi Carrier (MC) DS-CDMA compared to SC DS-CDMA. It is also observed that increasing the number of subcarriers does not affect much in MC DS-CDMA, which will definitely allow to minimize the delay spread which is a vital limitation of wireless communication system.

The paper presents upper bounds on the bit error rate (BER) of optimum combining in wireless systems with multiple cochannel interferers in a Rayleigh fading environment. The authors present closed-form expressions for the upper bound on the bit error rate with optimum combining, for any number of antennas and interferers, with coherent detection of BPSK and QAM signals, and differential detection of DPSK. They also present bounds on the performance gain of optimum combining over maximal ratio combining. These bounds are asymptotically tight with decreasing BER, and results show that the asymptotic gain is within 2 dB of the gain as determined by computer simulation for a variety of cases at a 10/sup -3/ BER. The closed-form expressions for the bound permit rapid calculation of the improvement with optimum combining for any number of interferers and antennas, as compared with the cpu hours previously required by Monte Carlo simulation. Thus, these bounds allow calculation of the performance of optimum combining under a variety of conditions where it was not possible previously, including analysis of the outage probability with shadow fading and the combined effect of adaptive arrays and dynamic channel assignment in mobile radio systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Rapidly growing demand for high data rates in wireless communication systems is the cause of the merging of Multiple Input Multiple Output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM) techniques. MIMO-OFDM technique needs Radio Frequency (RF) front end in each antenna, which is not effective for large dimensional antenna size. Therefore, RF front end on the receiver side will be simplified using a single RF technique based on the Electrically Steerable Parasitic Array Radiator (ESPAR) antenna. In real life, a channel cannot be ideal. Therefore, before the signal is transmitted, that signal must be coded to minimized errors when the data transmission process. Convolutional code is a coding technique that can detect and correct error bit (error control coding) and that it is expected to reduce the quantity of Bit Error Rate (BER). In this research, a simulation is designed to analyze single RF performance on the MIMO-OFDM system using Vertical Bell Laboratories Space-Time (VBLAST) detection for convolutional code encoder and Viterbi decoder. The result simulation shows that the channel estimation technique works well on the MIMO-OFDM system using single RF, which is shown in the magnitude and phase curves against the subcarrier index between the theory channel and the estimated channel are at almost the same points. VBLAST-ZF detector performance is shown in the BER curve against SNR, where the difference BER value for SNR value 10 dB between the theory channel and the estimated channel is 0.001499. Channel coding technique using convolutional code encoder and Viterbi decoder with a rate of ½ works well on the MIMO-OFDM system using single RF which is shown in the BER curve against SNR, where BER value with coding technique is smaller than BER value without coding technique.

Multiple transmit-receive antenna based wireless communication system is a well investigated area in the literature. However, within the scope of author’s knowledge there are few analytical frameworks which facilitate communication system design engineers to select the required transmit-receive antenna combination for a given quality of service (QoS) in terms of Bit Error Rate (BER) or Symbol Error Rate (SER). Most of such frameworks for Multiple-Input Multiple-Output (MIMO) wireless systems in the existing literature are lacking tightness between theoretical approximation and actual simulation results. The aim of investigation in this study is to provide theoretical expectation of receiver performance with MIMO wireless communication system within a given channel. In this study, new analytical performance bound frameworks with tighter lower bounds have been presented for different receivers for MIMO systems. On the basis of the presented analytical framework, a simulation platform has been established. The channel state information as well as expected quality of service is assumed to be known for simplicity. Rayleigh fading channel has been considered within simulation platform. Simulation results show that the proposed frameworks provide degree of tightness up to 100 times at Signal to Noise Ratio (SNR) 20 dB for (2x2) MIMO system in comparison to the existing frameworks. Few other MIMO antenna combinations have been considered in the evaluation process of the proposed framework.

Wireless communication systems are of paramount importance in the telecommunication infrastructure and have been playing a leading role in the development of nations. However, the system is characterized by multipath propagation effects that degrade the performance of the system. Amplify Quantize and Forward (AQF) cooperative relaying technique used to address the problem is characterized by poor performance due to signal amplification and obstruction along the propagating channel between the relay and destination. Hence, in this paper, the Enhancement of AQF (E-AQF) cooperative relaying protocol is carried out to improve the performance of the Conventional AQF (C-AQF) technique in a wireless communication system. The transmitted signal from the sourceis received at the relay node and the received signal is made to pass through spectral subtraction. The resultant signal is amplified using relay gain. The amplified signal at the relay node is quantized using uniform quantization before being forwarded to the destination during second hop transmission using angular beamforming. The multiple copies of the received signal at a varying path (L = 2, 4) are combined at the destination using Equal Gain Combiner (EGC). Mathematical expressions of Bit Error Rate (BER) and Throughput (TP) are derived using PDF. The performance of the proposed technique is evaluated using BER and TP by comparing it with the C-AQF cooperative relay technique. The proposed E-AQF gave better performance with reduced BER and increased TP than the C-AQF. The proposed E-AQF can be deployed to improve the performance of wireless communication systems.

– This paper analyses the performance of Multiple Input Multiple Output (MIMO) wireless communication system by combining it with an efficient algorithm Diagonal Reduction (DR). DR is a powerful tool to achieve more efficiently a high performance with less complexity. This paper proposes a DR algorithm in order to reduce its complexity named Greedy Diagonal Reduction (GDR) algorithm which gives reduced complexity with efficient performance at the receiver using the MATLAB communication tool box version 7.0 as a simulation tool. From the simulation results of various reduction algorithms it is observed that, DR can reduce the number of iterations using size reduction operations. Proposed DR algorithm gives identical Bit Error Rate (BER) performance with LLL algorithms when applied to Successive Interference cancellation (SIC) decoding. Greedy DR reduces the computational complexity in Multiple Input Multiple Output systems by improving the efficiency in terms of size reduction operations. Sphere Decoding (SD) technique gives better BER performance on comparing with Successive Interference cancellation decoding technique.

Modulation techniques in 5G wireless communication systems play a crucial role in meeting demands for higher data rates, lower latency, and improved connectivity. This involves optimizing power spectral density (PSD), enhancing data transmission reliability, and reducing bit error rates (BER) and interference. The objective of this paper is to evaluate primary modulation schemes used in 5G—Orthogonal Frequency Division Multiplexing (OFDM), Filter-Orthogonal Frequency Division Multiplexing (F-OFDM), Filter Bank Multi-Carrier (FBMC), and Universal Filtered Multi-Carrier (UFMC)—based on performance metrics such as PSD, BER, and signal-to-noise ratio (SNR) using MATLAB. OFDM demonstrates low BER at high SNR but faces degradation at lower SNRs, necessitating a higher SNR for maintaining low BER. F-OFDM improves BER in noisy environments through reduced out-of-band emissions and improved spectral efficiency. FBMC shows lower BER than OFDM, especially in multipath fading scenarios, despite its higher complexity. UFMC provides balanced performance with moderate BER across varying SNRs, offering a trade-off between simplicity and efficiency, with stable BER and enhanced spectral efficiency, and reduced latency compared to OFDM. Each modulation scheme in 5G presents specific strengths and weaknesses. OFDM is robust and widely used, while F-OFDM, FBMC, and UFMC enhance spectral efficiency, BER, and SNR management. Selecting the appropriate technique depends on network requirements, with MATLAB simulations playing a crucial role in optimizing 5G network performance.

SummaryWe consider the problem of bit error rate (BER) degradation because of the power gain imbalance between horizontal (H)‐polarization and vertical (V)‐polarization components in an orthogonal dual‐polarization transmission system. To alleviate the aforementioned BER degradation problem, we propose a non‐orthogonal polarization‐domain rotation scheme where the axes of H‐polarization and V‐polarization components are rotated with different angles at the transmitter and de‐rotated at the receiver. In addition, in order to assess the effectiveness of the polarization‐domain rotation scheme, we derive the closed‐form BER expression under a practical dual‐polarized channel model, which is represented by cross‐polarization ratio and co‐polarization ratio (CPR). We also derive the approximated BER expressions for the two asymptotic values of CPR: balanced CPR and infinite CPR. With the derived BER expressions, we find the optimal rotation angles that jointly minimize the BER. According to the numerical results, it is shown that about 3dB Eb/N0 gain is obtained at the BER of 10−4 and the CPR of 10dB by the polarization‐domain rotation scheme with optimal rotation angles compared with the conventional orthogonal dual‐polarization transmission. Copyright © 2015 John Wiley &amp; Sons, Ltd.