Multicarrier Transmission Technique Research Articles

Deep Learning Aided 5G Channel Estimation

Abstract: Wireless communications involves the transfer of voiceand data without a cable or wires. It uses orthogonal frequencydivision multiplexing, also known as a multicarrier transmission technique. In multiple input multiple output (MIMO) wireless communication (4G and 5G technologies), channel estimation is crucial. Multiple antennas are used at both the transmit and receive sides ofa MIMO system to increase spectral efficiency and reliability. In 5G channel estimation is performed to improve the accuracy of the received signal. Least-squares estimation is a cheap method with relatively large channel estimationerrors, but it is supported in this work by using a new channel estimation method that leverages deep learning. LS (least squares) and MMSE (minimum mean squared error) are two popular traditional approaches to channel estimation, but deep learning provides much more accurate results than previous channel estimation methods.

Spectrum analysis of OFDM versus FBMC in 5G mobile communications

With the demand for mobile data traffic, multi-carrier transmission techniques are highly attractive for all-new wireless communication systems, which divides data into many components and sends each of these components via a different carrier signal. So far, orthogonal frequency division multiplexing (OFDM) and filter bank multi-carrier (FBMC) techniques are the dominant waveform contenders. A number of studies have been made and failed to give a complete comparison where they did not consider various conditions altogether. Therefore, this paper addresses a complete comparative analysis of OFDM and FBMC, performed based on spectral efficiency, modulation, demodulation, power spectral densities, and peak to average power ratio comparison, all simulated using Matlab and GNU’s not unix radio (GNU-radio) software.

Index and mode modulated orthogonal frequency division multiplexing with enhanced spectral efficiency

AbstractIndex modulation aided orthogonal frequency division multiplexing (OFDM‐IM) is a potential multicarrier transmission technique for wireless data transmission systems due to its attractive error performance and energy efficiency. However, it fails to cope with increasing demand of high data rate in upcoming mobile data services, mainly, due to the lower spectral efficiency. In this communication, an efficient transmission technique, called index and mode modulation OFDM, is proposed that delivers additional information through permutations of multiple modes and indexed bits patterns resulting in higher spectral efficiency. For the proposed technique, a low complexity log‐likelihood ratio detector with suitable algorithm is designed and its computational complexity has been analysed. The simulation results indicate improved performance of this newly proposed scheme in terms of spectral efficiency, bit error rate, as well as energy efficiency over other existing index modulated and multiple mode based OFDM schemes, while maintaining considerably low computational complexity in detection. That proclaims the scheme as a potential transmission technique to meet the data transmission challenges in 5G and beyond.

Multicarrier technique for 5G massive MIMO system based on CDMA and CMFB

Filterbank multicarrier (FBMC) is an effective method for modulation over massive multiple-input multiple-output (MIMO) channels in the future fifth generation wireless networks. This multicarrier technique provides high spectral efficiency, and it is resilient against synchronization errors compared to the well-known orthogonal frequency division multiplexing technique. This paper introduces a new technique, that combines the Code-division multiple-access (CDMA) and cosine modulated filter banks, a specific class of FBMC, to massive MIMO communication systems. In the proposed technique, the data symbols are transmitted on different sub-bands and also, they are spread in each sub-band by CDMA code. The proposed technique reduces the interference between data symbols, which consequently improves bit-error-rate (BER) performance. Simulation results show that the overall BER performance of the proposed multicarrier transmission technique is significantly enhanced. The results obtained show that as the number of base station antennas increases, different channel distortions are averaged out, thus BER decreases (in average by 10–2) for the same signal-to-noise ratio.

Overview on PAPR reduction techniques in OFDM-IM

This paper is concerned with the novel multicarrier transmission technique, Orthogonal Frequency Division Multiplexing (OFDM) based on Index Modulation (IM), which acts as an alternative for conventional OFDM. The system generally shows improvements over conventional OFDM in achieving lower bit error rate, higher spectral efficiency, and better energy efficiency. Making it useful for various applications such as battery-powered communication devices, visible light communication, massive machine type communications, etc. Accordingly, becoming a suitable candidate for the next generation of wireless communication. In spite of its advantages over conventional OFDM, and due to their similarity, OFDM-IM suffers from the problem of high Peak to Average Power Ratio (PAPR). In this paper, a thorough review of the published works regarding PAPR reduction schemes in OFDM-IM is presented.

A Modified SLM Scheme for PAPR Reduction of UFMC Systems

One of the most promising 5G waveform candidates is the universal-filtered multicarrier system (UFMC). The UFMC system reduces the out-of-band (OoB) emission, bringing about higher spectral efficiency. This is assumed to reach robustness against frequency offset and low latency. Although, as aforementioned, the UFMC system offers many advantages, it lacks high peak-to-average power ratio (PAPR) as a multicarrier transmission technique. This research paper tackles two approaches; firstly, RCS, by developing a simulated conventional SLM system, with modifications to generate the same number of waveforms, while using fewer UFMC modulators. Secondly, by developing a simulated conventional SLM system, with modifications using the same number of modulators to generate more waveforms that would be generated in the conventional scheme. The two sets of results from the proposed M-SLM scheme are compared to each other, and to other PAPR reduction schemes using OFDM and UFMC. To reduce PAPR in UFMC systems, (M-SLM) scheme with low complexity is proposed. The essence of the proposed M-SLM scheme is represented in making use of the cyclically shifting process and FMC modulator’s linearity property. The proposed M-SLM scheme uses Um UFMC modulators to produce Uw alternative UFMC waveforms, where Uw = Um (2Um − 1). As a result, drawing a comparison with existing SLM based PAPR reduction schemes for UFMC systems; the proposed M-SLM scheme's computational complexity is reduced. Finally, there is a comparison between the proposed M-SLM scheme and the schemes there in the literature according to PAPR reduction ability.

Orthogonal frequency division multiplexing with cascade index modulation

As an emerging technique, index modulation (IM) can improve the system bit error rate (BER) performance due to the robustness of index bits over conventional modulated symbol bits. The existing IM aided orthogonal frequency division multiplexing (OFDM) schemes only employ one index modulator at the transmitter, which transmits a small amount of index bits in each transmission. In this paper, a novel IM technique, called cascade IM (CIM), is proposed to increase the proportion of the index bits in the transmission by combining the conventional IM with the multiple-mode IM together. Subcarrier-wise and subblock-wise CIM schemes are proposed to achieve different spectral efficiency and diversity order for diverse scenarios in the next generation wireless communication networks. The optimal subcarrier-wise maximum likelihood detector is proposed for OFDM-CIM. To reduce the demodulation complexity, a novel tree search based and an iterative log-likelihood ratio based detectors, which can avoid illegal index patterns in the search process, are developed for OFDM-CIM. Monte Carlo simulations show that the proposed scheme achieves better BER performance than OFDM-IM and appears as a competitive candidate of multi-carrier transmission techniques for next generation wireless communication networks.

A Simple Multicarrier Transmission Technique Combining Transmit Diversity and Data Multiplexing for Non-Orthogonal Multiple Access

Since the intra-group co-channel interference is introduced intentionally by the non-orthogonal multiple access (NOMA) technique, the reliability of NOMA based networks is limited by far users, while the sum-rate is mainly contributed by near users. In this paper, a NOMA based multiband scheduling policy is proposed to overcome this problem. Unlike conventional NOMA where all users are served in a single frequency band, the proposed scheme divides the entire band into multiple sub-bands, and accommodates the near and far users in different manners by exploring the sub-bands. Particularly, the far users employ repetition-based transmission in all sub-bands, and the maximum ratio combination (MRC) is integrated with successive interference cancellation (SIC) to jointly decode their intended symbols. Closed-form expression of the achievable sum-rate of the proposed scheme is derived, and the outage performance is characterized by the derived upper-bounded outage probability. Numerical results show that the proposed scheme enables NOMA systems to achieve both high reliability and high sum-rate.

WITHDRAWN: MIMO-OFDM with index modulation for 5G networks

With the developing interest for high data rate applications requiring little to no effort, wireless communication is the most significant territory of exploration, the response to the current issue is OFDM. Multicarrier transmission techniques like OFDM with IM (Index Modulation) is the most suitable alternative over traditional OFDM. Transmitting information that is at the files of dynamic subcarriers is an additional hotspot for information. In this paper, we make it clear about the execution and error performance assessment of the MIMO-OFDM-IM framework material to the next generation i.e., 5G wireless networks. MMSE and ZF of MIMO-OFDM-IM are being anticipated and their hypothetical execution has been inspected for VBLAST and IM and showed through broad PC models. MIMO-OFDM-IM framework gives an intriguing compromise between error performance and phantom proficiency since it achieves preferable error performance over MIMO-OFDM by using various types of detectors .

Bit Error Rate Performance of Ofdm Utilising Differentially Encoded 16 Star Qam with Differentially Coherent Demodulation in Awgn, Frequency Flat and Two-Path Fading Channels.(Dept.E)

The multicarrier transmission technique known as Orthogonal Frequency Division Multiplexing (OFDM) was devised in the 1960's for voiceband data transmission. Today there are two principles FDM applications, one is for the high speed digital subscriber loop and the other is for the broadcasting of digital audio and video signals. It will consider the use of OFDM for high-bit rate wireless applications. In order to improve spectral efficiency, 16 star quadrature amplitude modulation (QAM) is employed to modulate the parallel carriers in place of the usual quadrature phase shift -keying (QPSK). This paper investigates the bit error rate (BER) performance of OFDM utilising differentially encoded (DE) 16 star QAM and differentially coherent demodulation in frequency flat and two-path fading channels via Monte Carlo simulation. The BER performance of OFDM is also compared with equivalent single carrier systems.

Análisis de la técnica UFMC en un canal multitrayecto y usando estimación de canal

UFMC (Universal Filtered Multi-Carrier) is a novel multi-carrier transmission technique that aims to replace the OFDM (Orthogonal Frequency Division Multiplexing) modulation technique for fifth generation (5G) wireless communication systems. UFMC, being a generalization of OFDM and FBMC (Filter Bank Multicarrier), combines the advantages of these systems and at the same time avoids their main disadvantages. Using a Matlab simulation, this article presents an analysis of the robustness of UFMC against fading effects of multipath channels without using a CP (cyclic prefix). The behavior of the UFMC system is analyzed in terms of the PSD (Power Spectral Density), BER (Bit Error Rate) and MSE (Mean Square Error). The results show that UFMC reduces the out-band side lobes produced in the PSD of the processed signal. Also, it is shown that the pilot-assisted channel estimation method applied in OFDM systems can also be applied in UFMC systems.

Orthogonal frequency division multiplexing with power distribution index modulation

Orthogonal frequency division multiplexing with index modulation (OFDM-IM) is a promising multicarrier transmission technique that exploits both conventional modulation and the indices of active subcarriers for data transmission. In this Letter, the authors propose OFDM with power distribution index modulation (OFDM-PIM) where a unique power distribution technique is applied to index modulated subcarriers. Furthermore, we propose OFDM with in-phase/quadrature PIM (OFDM-I/Q-PIM) which performs the same power distribution process on the real and imaginary parts of the data symbols, independently. Average bit error performances of OFDM-PIM and OFDM-I/Q-PIM are obtained and the superiority of the proposed schemes over reference schemes is demonstrated via extensive computer simulations.

On Effects of Frequency Offset on Simulink Model of OFDM

OFDM is a multicarrier transmission technique, widely preferred due to advantages like high data rate, less bandwidth consumption and channel robustness. IEEE 802.11a standard uses conventional OFDM which uses IFFT for generating orthogonal carriers and multiplexing. Due to extra bandwidth consumption by cyclic prefix in conventional OFDM, DWT has now emerged as new alternative over FFT. It offers advantages like increased spectral efficiency, better orthogonality and less bit error rate. Performance degradation due to frequency offsets has been reported in literature. Carrier frequency offset (CFO) arises due to Doppler shift and imperfect synchronisation of transmitter and receiver. CFO results in inter-carrier interference that effect BER. In this paper, we investigated the offset effect on conventional and DWT-based OFDM under different communication channels (AWGN and Rayleigh). Effect of different modulation techniques and wavelets on DWT-OFDM model is also analysed.

SαS noise suppression for OFDM wireless communication in rayleight channel

Orthogonal frequency division multiplexing (OFDM) is a form of multi-carrier transmission technique widely used in the modern wireless network to achieve high-speed data transmission with good spectral efficiency. However, in impulsive noise environement BER performances of these systems, originally designed for a Gaussian noise model, are much degraded. In this paper, a new symmetric-alpha-stable (SαS) noise suppression technique based conjointly on adaptive modulation, convolutional coding (AMC) and Recursive Least Square (RLS) filtering is presented. The proposed scheme is applied on OFDM system in Rayleigh fading channel. The transmissions are analyzed under different combinations of digital modulation schemes (BPSK, QPSK, 16-QAM, 64-QAM) and convolutional code rates (1/2, 2/3, 3/4). Simulation results show that our proposed hybrid technique provides effective impulsive noise cancelation in OFDM system and exhibits better BER performance.

Autocorrelation Method for Cyclic Prefix OFDM Estimation

A radio system design providing various data service needs becomes one of the Software Defined Radio (SDR) system advantages. SDR technology applies software functions further to be run in hardware platforms. The need for services with greater data rates can be resolved by using multi-carrier transmission techniques, one of which is the Orthogonal Frequency Division Multiplexing (OFDM) technique. This paper discusses the detection of OFDM signals and their parameters. Multi-carrier transmission can prevent Inter-Symbol Interference (ISI) occurrence due to multi-path fading effect. The recognition can classify the correctly received signals, including the signal conditions mixed with AWGN noise. The autocorrelation method was used to estimate the OFDM parameters, namely the one symbol duration and the cyclic prefix duration. The detected cyclic prefix durations were 1/2, 1/4, 1/8, and 1/16. This method is very simple, because with the cyclic prefix presence, a different signal peak will be detected to further estimate the cyclic prefix duration. The results show the correlation method performance can detect one symbol duration with 100%, accuracy, starting at SNR 0 dB, whereas the cyclic prefix duration accuracy rate is getting more accurate by using a less cyclic prefix duration, which is 1/16 of the total symbol duration.

Enhancing Performance of Orthogonal Frequency Division Multiplexing (OFDM) Based On Fast Fourier Transform (FFT) In Wireless Communication System

Orthogonal Frequency Division Multiplexing (OFDM) is one of the multicarrier transmission techniques used in wireless communication system. It has many benefits such as robust in channel fading and has high spectral density. The main objective of OFDM implementation in wireless communication system is to achieve less or zero Bit Error Rate (BER). However, OFDM design complexity, requirement and selection of the suitable modulation method are among the current issues. Thus, this paper aims to investigate the performance of OFDM in wireless communication by developing two OFDM based system designs. The transmitter, channel and receiver are designed based on OFDM system principles. Forward Error Correction (FEC) method is applied to reduce the BER. Both OFDM designs produce less BER with zero BER for the second OFDM design. The investigation study shows that the performance of OFDM can be enhanced by applying Fast Fourier Transform (FFT) technique. Zero BER can be achieved if the suitable modulation scheme is applied in the system. The developed designs are not complex, suitable to be applied for IEEE 802.11 standard. The BER performance can be influenced by the types of channels, signal to noise ratio (SNR) and various modulation schemes. Thus, this study can be used as a guidance to implement the OFDM in the current or future wireless communication system.

Performance of MiMo-OFDM Systems in Rayleigh Channel

<em>Along with the development of wireless communication makes the increasing demand for obtaining quality services and better range, bandwidth-efficient and reliable system. OFDM is a multicarrier transmission technique to overcome multipath fading, which may result in intersymbol interference (ISI). On the other hand there is the antenna system with the use of multiple antennas at the transmitter and receiver that can also be overcome multipath fading,ie Multiple Input Multiple Output (MIMO) to increase channel capacity and diversity gain. MIMO techniques used in this Final adaldah Space Time Block Code. Simulation aims to simulate and analyze the MIMO OFDM technique using space-time block code against the influence of the number of subcarriers and influence user speed in AWGN channel and Rayleigh. The simulation results based on the number of subcarriers in AWGN channel, the best performance is obtained by subcarrier number 256. With BPSK and QPSK modulation obtained BER = 6 10-4 when SNR 4 dB. Simulation based on Rayleigh channel obtained when BER = 9.7 10-5 with BPSK modulation. Based on the comparison of the greater frequency doppler given doppler frequency, resulting in BER generated even greater, because the state of the canal will be getting worse.</em>

Low-Complexity Detection for Multiple-Mode OFDM with Index Modulation

Multiple-mode orthogonal frequency division multiplexing with index modulation (MM-OFDM-IM) is a recently proposed multicarrier transmission technique, which transmits distinguishable constellations (modes) according to their full permutations. For an uncoded system, the maximum-likelihood (ML) detector achieves the optimal performance, but its computational complexity is extremely high due to a large number of symbol modes. Existing low-complexity detectors may output an illegal mode permutation, which leads to catastrophic errors in the demodulation. redIt is well known that sphere decoding algorithms can reduce the computational complexity effectively and achieve near-ML bit error rate (BER) performance. In this paper, employing a sphere-decoding-like algorithm, we propose a novel detector, which can achieve near-ML performance with considerably low computational complexity. For coded MM-OFDM-IM systems, we propose a simplified log-likelihood ratio (LLR) calculation algorithm to achieve near-optimal coded BER performance with considerably low computational complexity. Computer simulation and numerical results demonstrate that the proposed detectors can achieve outstanding performance at the cost of low computational complexity.

An Enhanced Peak to Average Power Ratio Reduction Scheme for Interleaved and Sub-Band Orthogonal Frequency-Division Multiple Access Frameworks with Low Complexity

Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier transmission technique which has the major drawback namely Peak to Average Power Ratio (PAPR). The high PAPR influences the efficiency of the power amplifier. The Selected Level Mapping (SLM) gives reduced PAPR contrasted with different strategies but the complexity is high due to the necessity of various Inverse Fast Fourier Transform (IFFTs). With the end goal to reduce the complexity, the proposed design requires only one IFFT, the candidate signals are produced by cyclic shifting the original time domain signal then multiplying with the distinctive genuine positive numbers. At that point the candidate with most minimal PAPR is chosen for transmission.

GFDM Based Wireless Powered Communication for Cooperative Relay System

Green and sustainable communications are crucial for cellular devices and the Internet of Things (IoT) devices in the fifth generation (5G) mobile communication system. Wireless-powered communication (WPC) provides a successful technical paradigm to support wireless information transmission for mobile devices by using harvested radio-frequency (RF) energy. In the meantime, non-orthogonal multicarrier transmission techniques, typically represented by the generalized frequency-division multiplexing (GFDM), can not only enhance spectrum efficiency but also improve the flexibility of resource allocation due to its fine-granularity sub-block. In this paper, a GFDM-based cooperative relay system model is proposed to improve the quality of experience of the cell-edge user. Specifically, the system is composed of one source node, one destination node (cell-edge user), and one relay node. The source node transmits a signal to the destination node and the relay node. The relay node performs information transmission and power transfer to the destination node by using different GFDM sub-block sets. The destination node combines the signals from the source node and relay node. In order to maximize the information rate at the destination node subject to the minimum harvested energy, a joint sub-block, sub-block power, and subslot allocation-based WPC scheme is proposed. To solve the non-convex optimization problem, an iterative algorithm is proposed and its effectiveness is validated by simulations. The simulation results demonstrate that the GFDM-based WPC scheme outperforms the orthogonal frequency-division multiplexing (OFDM), and the subslot optimization can significantly increase the information rate at the destination node.