Multicarrier Transmission Technique Research Articles

CO-OFDM and DP-QPSK Based DWDM Optical Wireless Communication System

Abstract The 5 G technology provides a promising solution for future broadband networks. It requires access to high-speed wireless services for systems at anytime and anywhere. For adapting the 5 G services, this paper proposes an optical wireless system with hybrid scheme of dual polarized Gbps dense wavelength division multiplexed (DWDM) system. The multi-carrier transmission technique such as coherent optical orthogonal frequency division multiplexing (CO-OFDM) has also been incorporated into the system. The frequency spacing for the DWDM system is taken 25, 50 and 100 GHz according to the ITU-T standard. Here the subcarriers of each channel are modulated with the dual polarized-quadrature phase shift keying (DP-QPSK) sequence. The information is transmitted with an overall data rate of 0.32 Tbps. The system is successfully demonstrated at different turbulence regime from clear weather to severe turbulence weather under Gamma-Gamma atmospheric turbulence channel model. Due to the high optical signal-to-noise ratio (OSNR) tolerance and high spectrum efficiency of the dual polarized multi-channel and multicarrier transmission technique, the link distance achieved is 2.9 km in clear weather, 2.6 km in moderate turbulence regime, 2.3 km in high turbulence regime and 0.9 km in severe turbulence regime. A comparison study with related works has been carried out. Mathematical modeling is also incorporated for detail analysis of the proposed system.

Desempeño de Controladores Inalámbricos Codificados Aplicados en Turbinas Eólicas Conectadas a una Smart Grid

<p>Actualmente, con el avance de las tecnologías de smart grid, la participación de las fuentes renovables en los sistemas energéticos está cambiando para atender las nuevas necesidades y aumentar la eficiencia de los sistemas. Con una visión del contexto de smart grid, este trabajo propone la revisión del moderno sistema de control inalámbrico propuesto basado en los generadores de inducción de jaula de ardilla conectados a la red eléctrica. El sistema de comunicación inalámbrico aplicado transmite las señales de potencia de referencia al controlador SCIG con la confiabilidad necesaria para asegurar la calidad de energía proporcionada por el generador eólico con codificación LDPC y OFDM. Los resultados de esta investigación respaldan la operatividad y las ventajas de la aplicación del sistema de control inalámbrico para plantas eólicas cuando son empleados requisitos y técnicas basados en la modulación digital y las técnicas de codificación.</p>

Low-Complexity LLR Calculation for OFDM With Index Modulation

Orthogonal frequency division multiplexing with index modulation (OFDM-IM) is a promising multicarrier transmission technique. In OFDM-IM, only a subset of subcarriers are activated to transmit modulated symbols and the indices of the activated subcarriers are used to convey information bits implicitly. In the coded OFDM-IM system, we need to calculate the log likelihood ratio (LLR) value of each bit, whose computational complexity is extremely high due to the dependence between the subcarriers caused by the subcarrier-index modulation. In this letter, we propose a novel simplified LLR calculation algorithm for OFDM-IM. Simulation results show that the proposed algorithm achieves near-optimal coded bit error rate performance with considerably low computational complexity.

Orthogonality Measurent of OFDM Signal

<p>In recent days, Orthogonal Frequency Division Multiplexing is the technique to transmit and receive the signal without any overlapping of the signal. OFDM is also a multiplexing technique as well as modulation technique. It is a multi-carrier transmission technique in which single high data stream is divided into a number of lower rate streams that are transmitted simultaneous over some narrow sub channel. In general, OFDM avoids Inter-Symbol Interference (ISI), Inter-Carrier Interference (ICI) and fault transmissions between source and destination node. To measure the performance of the system by using the parameters like Bit Error rate (BER), Spectrum analysis and signal strength detection. Based on the parameters the best system can be identified.</p>

TCM for OFDM-IM

Orthogonal frequency division multiplexing (OFDM) with index modulation (IM) is a multicarrier transmission technique for frequency-selective fading channels. Although it is energy and spectral efficient, its performance may not be satisfactory as some active subcarriers can be suppressed by fading. In this letter, we consider trellis coded modulation (TCM) for OFDM-IM in order to improve the detection performance of active subcarriers by increasing the Hamming distance between index symbols. We devise mapping rules for TCM for two cases and it is shown that the diversity order can be improved, which results in a lower probability of index error.

A new hybrid multicarrier transmission technique with iterative frequency domain detection

The growing progress in wireless communication services led to a demand in high data rates, spectral efficiency and flexibility requirements. The Block-Windowed Burst Orthogonal Frequency Division Multiplexing (BWB-OFDM) technique has been recently proposed to face these demands. This technique employs smoother, non-rectangular windows, allowing a power spectral density similar to the filtered OFDM approach, thus achieving high spectral efficiency; also, it packs together several OFDM symbols, with the addition of a sole zero-padding to accommodate the multipath channel’s propagation delay, thereby improving power efficiency. However, BWB-OFDM has the same drawbacks of OFDM when transmitting over hostile channel conditions, namely the performance degradation due to deep fades associated to severe frequency-selective channels.This paper proposes a new Time Interleaved BWB-OFDM (TIBWB-OFDM) technique that performs interleaving on the time-samples of each BWB-OFDM block, creating a kind of diversity effect at the frequency domain, granting a much better resilience against deep inband fades, while keeping all the mentioned advantages of BWB-OFDM at the cost of no added complexity. Also, by regarding TIBWB-OFDM as a hybrid technique combining single-carrier and multicarrier characteristics, this paper also proposes the use of non-linear frequency domain equalizers based on the Iterative Block Frequency Domain Equalization (IB-DFE) concept for TIBWB-OFDM detection. It is shown that noteworthy improvements can be achieved in bit error rate (BER) performance compared to conventional OFDM schemes when employing typical zero-forcing (ZF) and minimum mean-square error (MMSE) linear equalizers.

A Survey of Optical Carrier Generation Techniques for Terabit Capacity Elastic Optical Networks

Elastic optical networks (EON) have been proposed to meet the network capacity and dynamicity challenges. Hardware and software resource optimization and re-configurability are key enablers for EONs. Recently, innovative multi-carrier transmission techniques have been extensively investigated to realize high capacity (Tb/s) flexible transceivers. In addition to standard telecommunication lasers, optical carrier generators based on optical frequency combs (OFC) have also been considered with expectations of reduced cost and inventory, improved spectral efficiency, and flexibility. A wide range of OFC generation techniques have been proposed in the literature over the past few years. It is imperative to summarize the state of the art, compare and assess these diverse techniques from a practical perspective. In this survey, we identify salient features of optical multicarrier generators, review and compare these techniques both from a physical and network layer perspective. OFC demultiplexing/filtering techniques have also been reviewed. In addition to transmission performance, the impact of such sources on the network performance and real-world deployment strategies with reference to cost, power consumption, and level of flexibility have also been discussed. Field trials, integrated solutions, and flexibility demonstrations are also reported. Finally, open issues and possible future directions that can lead to real network deployment are highlighted.

Resource block filtered-OFDM as a multi-carrier transmission scheme for 5G

The fifth generation of mobile communications, which has higher requirements for data rate and spectral efficiency, will be a key technology for future wireless communication systems. Therefore, based on the current spectral division, the use of idle spectra of low-frequency bands is needed to address 5G mobile scenarios. The side lobe in frequency division multiplexing (OFDM), which is widely adopted in 4G, is so high that it produces adjacent channel interference. The addition a cyclic prefix is necessary to resolve such an interference problem; however, this leads to spectral efficiency degradation. Therefore, this study presents a new multi-carrier transmission technique for future wireless communication systems. Intuited by the filter bank based multi-carrier (FBMC) and the universal-filtered multi-carrier (UFMC), we proposed band resource block filtered orthogonal frequency division multiplexing (RB F-OFDM). RB F-OFDM retains the advantages of OFDM; moreover, its sideband has rapid attenuation, its energy is more concentrated, and it can avoid inter-carrier interference (ICI). When adjacent channel interference exists, the performance of RB F-OFDM is better than that of OFDM and UFMC.

Amplitude reconstruction of clipped OFDM by using DFT-based least squares

OFDM is an e ective multicarrier transmission technique with one primary disadvantage; it su ers from high Peak-to-Average Power Ratio (PAPR). Although clipping and ltering is a simple and e ective method for PAPR reduction, it makes in-band and out-of-band noise, which degrades the bit error rate performance and spectral eficiency. Publications on this subject show that clipped samples could be reconstructed at the receiver by using oversampled signal and bandwidth expansion. By building on published literature, this paper aims to achieve a low-complexity method. The proposed method has complexity order of O(L2) to solve linear system, where L indicates the number of clipped samples. Simulation results con rm that our proposed method leads to both a better biterror rate performance and a lower complexity than similar methods. These results also show that our method o ers adequate performance, especially at low clipping ratios.

FBMC vs OFDM Waveform Contenders for 5G Wireless Communication System

The multicarrier transmission techniques have been the most beguiling one for the development of wireless communication systems like 4G, Long Term evolution and now the successor 5G. For 5G or fifth generation wireless communication, Orthogonal Frequency Division Multiplexing (OFDM) and Filter Bank Multi carrier modulation (FBMC) are the dominant waveform contenders. In this research paper, the disadvantages of OFDM have been addressed and it has shown that filter bank multicarrier (FBMC) could be a more effective solution. The comparative analysis of FBMC and OFDM has been performed based on Power Spectral Densities, sub channels, computational complexity and prototype filter comparison simulated using MATLAB.

Low-Complexity Subcarrier-Wise Detection for MIMO-OFDM With Index Modulation

Multiple-input multiple-output orthogonal frequency division multiplexing with index modulation (MIMO-OFDM-IM) is a relatively new multicarrier transmission technique for the MIMO systems to achieve both energy and spectral efficiency. However, due to the dependence of subcarrier symbols introduced by the index modulation, existing MIMO detection techniques cannot be applied in MIMO-OFDM-IM as it will lead to erroneous detection on index information of the active subcarriers and further deteriorate the system performance. In this paper, we first develop an optimal detection algorithm with reduced complexity for MIMO-OFDM-IM by performing the subcarrier-wise detection under the constraint on the legal subcarrier combination within each OFDM-IM subblock. To further reduce the computational complexity, we then propose a low-complexity subcarrier-wise algorithm based on the deterministic sequential Monte Carlo technique to achieve near-optimal detection for MIMO-OFDM-IM. Specifically, the near-optimal detector applies the QR decomposition to generate an upper triangular structure and draw antenna-wise samples at the subcarrier level. Computational simulations and complexity analysis show that the proposed algorithms provide similar performance to optimal one with reduced computational complexity.

Error Probability Analysis of OFDM-IM With Carrier Frequency Offset

OFDM-IM, which uses the indices of active subcarriers to carry additional information bits, is a novel multi-carrier transmission technique. In this letter, by exploiting the special design of OFDM-IM, we propose an analytical approach to evaluate the error probability of OFDM-IM subject to carrier frequency offset (CFO) in fading channels, where the inter-carrier interference (ICI) is properly divided into two parts: the intra-subblock ICI and the inter-subblocks ICI. Simulation results illustrate that the results of theoretical analysis are quite accurate, and OFDM-IM outperforms the conventional OFDM when CFO exists.

UFMC 시스템에서 CFO의 영향

The UFMC(Universal Filtered Multi-Carrier) is one of multi-carrier transmission technique as a candidate of transmission method for the recent 5G communication system. The UFMC can be considered as the system which has both the advantages of OFDM(Orthogonal Frequency Division Multiplex) and the simplicity of FBMC(Filter Bank Multi-Carrier). CFO(Carrier Frequency Offset) causes the problem to lower the BER performance due to a mismatch between the sub-carriers in multi-carrier transmission scheme. The effect of CFO on UFMC is not greater than the OFDM. But it still degrades the system performance caused by interference between the sub-band. In this paper, we analyze the SNR degradation due to changes in the value of EsNo and CFO on UFMC system.

On Multiple-Input Multiple-Output OFDM with Index Modulation for Next Generation Wireless Networks

Multiple-input multiple-output orthogonal frequency division multiplexing with index modulation (MIMO-OFDM-IM) is a novel multicarrier transmission technique which has been proposed recently as an alternative to classical MIMO-OFDM. In this scheme, OFDM with index modulation (OFDM-IM) concept is combined with MIMO transmission to take advantage of the benefits of these two techniques. In this paper, we shed light on the implementation and error performance analysis of the MIMO-OFDM-IM scheme for next generation 5G wireless networks. Maximum likelihood (ML), near-ML, simple minimum mean square error (MMSE) and ordered successive interference cancellation (OSIC) based MMSE detectors of MIMO-OFDM-IM are proposed and their theoretical performance is investigated. It has been shown via extensive computer simulations that MIMO-OFDM-IM scheme provides an interesting trade-off between error performance and spectral efficiency as well as it achieves considerably better error performance than classical MIMO-OFDM using different type detectors and under realistic conditions.

Performance Assessment of OFDM Utilizing FFT/DWT over Rician Channel Effected by CFO

Orthogonal Frequency Division Multiplexing (OFDM) is a popular kind of multi-carrier based transmission technique that has found its applications in some wireless and wireline systems. But this system suffers from several facts that degrade its performance resulting in the interference of sub-carriers. Carrier Frequency Offset (CFO) is considered as one of the factor that causes interference in the system, leading to an Inter-Carrier Interference (ICI) between the carriers that results in a degradation in the performance factor of the system. In this research work, a comparative estimation is done on the Bit Error Rate (BER) performance of Discrete Wavelet Transform (DWT) OFDM and Fourier Transform (FFT) OFDM in the presence of CFO in both of the given systems. The research focuses mainly on the improvement of the BER in the system. The complete analysis is done by considering the channel to be Rician and the systems performance is estimated for some practical values of CFO. The complete simulation is done in the MATLAB. As the CFO increases the error in the system also increases, but still in that situation, DWT shows better improvement than the conventional system. The BER performance of OFDM systems shows improvement for all the diverse PSK modulation.

Multiple-Input Multiple-Output OFDM with Index Modulation

Orthogonal frequency division multiplexing with index modulation (OFDM-IM) is a novel multicarrier transmission technique which has been proposed as an alternative to classical OFDM. The main idea of OFDM-IM is the use of the indices of the active subcarriers in an OFDM system as an additional source of information. In this work, we propose multiple-input multiple-output OFDM-IM (MIMO-OFDM-IM) scheme by combining OFDM-IM and MIMO transmission techniques. The low complexity transceiver structure of the MIMO-OFDM-IM scheme is developed and it is shown via computer simulations that the proposed MIMO-OFDM-IM scheme achieves significantly better error performance than classical MIMO-OFDM for several different system configurations.

OFDM With Index Modulation Using Coordinate Interleaving

Orthogonal frequency division multiplexing with index modulation (OFDM-IM), which uses the indices of the active subcarriers to transmit data, is a recently proposed multicarrier transmission technique. In this letter, we propose coordinate interleaved OFDM-IM (CI-OFDM-IM) by combining OFDM-IM and space-time block codes with coordinate interleaving. In this scheme, the real and imaginary parts of the data symbols are transmitted over different active subcarriers to achieve an additional diversity gain. The average bit error probability (ABEP) of the proposed scheme is derived and its superiority over the reference systems is shown via computer simulations.

FBMC Modulation as a Possible Co-existence Facilitator for LTE Mobile Networks in 800 MHz Band

ABSTRACTThis paper proposes filter bank multicarrier transmission technique (FBMC) as means to minimize adjacent band interference from long-term evolution (LTE) user equipment operating in the frequency band 792–862 MHz to short-range devices in the band 863–870 MHz. Main FBMC benefits are presented through comparison with reference case of orthogonal frequency-division multiplexing. The key advantage of FBMC modulation in reported electromagnetic compatibility studies is derived from its low out-of-band leakage, which guarantees minimum harmful interference level between stations using adjacent channels. The problem was evaluated in two aspects: first, theoretical analysis using minimum coupling loss method, complemented with statistical Monte-Carlo analysis (using SEAMCAT software tool) in order to verify results obtained in theoretical approach.

A Review on OFDM and PAPR Reduction Techniques

OFDM is a multi carrier transmission technique where a single set of data is transmitted over a number of sub-carrier. OFDM takes the advantage of multi-path propagation and reduces the fading effect. The idea of OFDM is to split the total transmission bandwidth into a number of orthogonal subcarriers which reduces the inter-symbol-interference, power consumption and increases the capacity and efficiency of the system. Peak-Average-Power-Ratio (PAPR) is one of the dis-advantage of OFDM which reduces the efficiency of system. In first part of this review, We have describe the OFDM characteristics of signals and its designing by combining the different block and in next part of this work, we have consider the PAPR effect in OFDM signals and have compared and review a several PAPR Reduction Techniques. The aim of this article is to provide a comprehensive detail about the implementation of an OFDM System and to study the different PAPR reduction techniques.

Resource Allocation in Multiuser Multi-Carrier Cognitive Radio Network via Game and Supermarket Game Theory: Survey, Tutorial, and Open Research Directions

In this tutorial, we integrate the concept of cognitive radio technology into game theory and supermarket game theory to address the problem of resource allocation in multiuser multicarrier cognitive radio networks. In addition, multiuser multicarrier transmission technique is chosen as a candidate to study the resource allocation problem via game and supermarket game theory. This tutorial also includes various definitions, scenarios and examples related to (i) game theory (including both non-cooperative and cooperative games), (ii) supermarket game theory (including pricing, auction theory and oligopoly markets), and (iii) resource allocation in multicarrier techniques. Thus, interested readers can better understand the main tools that allow them to model the resource allocation problem in multicarrier networks via game and supermarket game theory. In this tutorial article, we first review the most fundamental concepts and architectures of CRNs and subsequently introduce the concepts of game theory, supermarket game theory and common solution to game models such as the Nash equilibrium and the Nash bargaining solution. Finally, a list of related studies is highlighted and compared in this tutorial.