Single Carrier Frequency Division Multiple Access Research Articles

BER Evaluation in LTE SC-FDMA under Multipath Channels

Channel equalization is very essential step in Single Carrier Frequency Division Multiple Access (SC-FDMA) transmission for overcoming the inter-symbol interference (ISI). Also, to evaluate the data-link and network scheduling of LTE technique, a particular channel modelling is crucial. Due to the techniques’ complexity and requirement of high bandwidth for data transmission in literature, we motivated to perform a comparative analysis for BER reduction in SCFDMA scheme with and without equalizer. Therefor, in order to enhance efficiency of performance and functionality of network application, due to huge demand for lower delay, latency and higher speed by the modern users, BER reduction is a significant factor for enhancing signal quality. The substantial focus of this research is to improve the uplink signal of LTE technology by using two type of linear equalization methods such as zero forcing (ZF) and minimum mean square error (MMSE) at receiver part. Moreover, analysis of BER and SNR for SC-FDMA systems are obtained under several channel models and two different sub-mapping. This evaluation is performed for SC-FDMA in uplink by aid of adaptive modulation techniques like QPSK. Finally, for evaluating the channel equalization efficiency with SC-FDMA and for investigating the response of an uplink transmitter, MATLAB framework, is applied in this study. The results reveal that PAPR reduction does not have significant impact on BER performance.

Towards energy efficient relay deployment in multi‐user LTE‐A networks

Communication using relay node (RN) cooperation is attractive research interest since it supports wide area coverage and high data rates. RNdeployment problem in multiple users long-term evolution-advanced (LTE-A) network is a challenging issue. In this article, the RN deployment problem for a single carrier-frequency division multiple access uplink system is considered. The total energy efficiency (EE) and average EE for multi-user single-relay in the LTE-A network are considered as the performance measures to select the optimum position of RN. Two types of users are deployed: guaranteed bit rate and non-guaranteed bit rate when performing load balancing that can influence the selection of the optimum position of RN. Simulation results show that the EE is increased by 10% based on load balancing compared to unbalanced loaded network. The optimum position of RN at 75% of a cell radius towards the cell edge can significantly improve the EE.

Matched Filter Based Spectrum Sensing Technique for 4G Cellular Network

Modern and fast developments of wireless technologies have directed to a great demand for resources. It can be seen in the study that the range of existing spectrum is not used effectively, therefore the frequency band should be observed to ensure proper usage and to have the information of primary or licensed user is very much essential. In this research work uplink of LTE (Long-Term Evolution) is observed through MF (Matched Filter) spectrum sensing technique of CR (Cognitive Radio) network. This method examines the existence of signals in minimum possible time, reduces the hindrances between secondary users, increases accurateness of sensing and provides finest choice of threshold. In Uplink the System model which is used is known as SC-FDMA (Single Carrier Frequency Division Multiple Access). Entire simulation/results are prepared in MATLAB environment. This study also provides graphical contrast of simulated and theoretical results of matched filter and energy detection technique.

Design and Evaluation of Test Waveforms Emitted by Portable Electronic Devices for Radiated Susceptibility Testing of Avionic Systems

Assessing the electromagnetic interference (EMI) susceptibility of aircraft systems to transmitting portable electronic devices is challenging. Existing waveforms for susceptibility testing use amplitude modulation: MIL-STD-461 recommends the use of pulse-modulated waveforms, whereas the radio technical commission for aeronautics recommends the use of filtered noise. The ability of such waveforms to represent the EMI of complex communication signals is unknown. This paper expands upon a parameter reduction process for the development of candidate waveforms that are representative of long-term evolution (LTE) signals: single-carrier frequency division multiple access, filtered noise, and pulsemodulated waveforms are proposed as candidate signals for radiated susceptibility testing. The waveforms were evaluated by measuring the EMI response of avionic equipment that was exposed to the waveforms in an anechoic chamber. The measured data were analyzed to determine whether the bandwidth and the peak-to-average power ratio had significant effects on the measured EMI compared to real LTE signals. The proposed method is general and can be used for other communication standards.

Low PAPR Filter Bank Single Carrier for 5G mMTC

Asynchronous transmission for 5G massive machine type communication (mMTC) reduces power consumption and provides longer battery life of mMTC devices compared to synchronous transmission because of less signaling interaction between the base station and mMTC devices. To reduce frequency leakage from other user devices, several waveforms based on modification on orthogonal frequency division multiple (OFDM) with low out-of-band (OOB) emission property has been proposed in 5G new radio. However, those waveforms are typically of high peak to average power ratio (PAPR) and it has been shown for those waveforms there is OOB emission regrowth for mMTC devices caused by nonlinear power amplify (PA). We propose a low PAPR filter bank single carrier frequency division multiple access (SC-FDMA) waveform, called LP-FBSC, which helps to resist OOB emission regrowth caused by nonlinear PA. Two filters are applied in one stream to achieve low PAPR and low OOB emission performance, where one filter is poly phase network (PPN) structure in time domain for low OOB emission purpose, and the other is applied at frequency domain with element-wise multiplication for low PAPR purpose. In addition, the proposed method introduces multiple streams for purpose of even further reduced PAPR, where the modulated data and filter coefficients of the other streams are determined from those of first stream. For Pi/2-BPSK and Pi/4-QPSK modulation, the PAPR for LP-FBSC can be as low as 2.6 dB and 4.2 dB while low OOB emission property being maintained.

A space wavelet block codes MIMO SC-WDMA systems

In this paper, a novel space-wavelet block codes single-carrier wavelet-division multiple access (SWBC SC-WDMA) multiple-input multiple-output (MIMO) transceiver is proposed. The proposed MIMO transceiver system improves both of the bit error rate (BER) performance and the peak-to-average power ratio (PAPR) performance. Bit error rate (BER) analysis of the proposed SWBC SC-WDMA system over a frequency selective Rayleigh fading channel is presented for the case of zero-forcing (ZF) equalization and QPSK modulation. Comparisons of the BER and PAPR performances between the proposed SWBC SC-WDMA system and the conventional space-frequency block codes single-carrier frequency-division multiple access (SFBC SC-FDMA) system are illustrated. The simulation results show that the proposed SWBC SC-WDMA system has superior improvements in both PAPR and the BER performances.

Novel Detectors for Massive MU-MIMO Communications

The massive multi-user multiple-input multiple-output (MU-MIMO) can be adapted to meet the increasing requirement of data throughput services in wireless transmission systems. The combination of the Single Carrier Frequency Division Multiple Access (SC-FDMA) with the massive MU-MIMO technology can be employed for the uplink transmission to meet the requirement of data rates and error performance. In this paper, for practical implementation, we integrate multi-user detection, Kalman channel estimation and turbo equalization and propose turbo detectors to solve the problem of huge computation load of matrix inversion at receiver side. The proposed low-complexity detectors are based on Neumann series expansion, successive over-relaxation (SOR), and symmetric successive over-relaxation (SSOR) principles. Simulation examples in the uplink scenario are given for the proposed low-complexity turbo detectors to demonstrate the comparisons and effectiveness of the proposed schemes.

A windowing-based joint user pairing and resource allocation algorithm for V-MIMO systems

In this paper, we investigate the user pairing and resource allocation (UP-RA) problem which is a critical step in uplink virtual multiple input multiple output (V-MIMO) systems. It becomes a joint problem under the framework of Long Term Evolution (LTE) where single carrier frequency division multiple access (SC-FDMA) is adopted in uplink due to the intrinsic consecutive resource allocation constraint imposed therein. Traditional two-step algorithms tackle this joint problem by separating the UP step and the RA step and turning them into two independent and successive procedures. Different from them, in this paper a windowing-based UP-RA algorithm is developed in which the user pairs are selected by maximizing their performance on a series of contiguous RBs rather than a single one as discussed in those traditional algorithms. With the windowing technique introduced in the new algorithm heuristically, improved performance in uplink V-MIMO systems can be achieved. In addition, we provide the relationship between the performance and the window size, and present that the window size can be selected adaptively to further exploit the diversity gain. Furthermore, to corroborate the universal validity of the proposed windowing technique, another algorithm named pairing and extension (P&E) is also modified accordingly by it. Corresponding simulation results manifest the great potential of the windowing technique to be applied to other general two-step algorithms in V-MIMO systems and improve their performances.

Companding techniques for SC-FDMA and sensor network applications

ABSTRACT The large Peak-to-Average Power Ratio (PAPR) is a serious problem in wireless communication systems for mobile and sensor network applications. This paper presents efficient non-linear techniques to solve the large PAPR problem in Single-Carrier Frequency Division Multiple Access (SC-FDMA) system and Wireless Sensor Network (WSN) systems. The performance of the proposed techniques is investigated over a realistic channel model. Simulation results reveal PAPR reduction while preserving low Bit Error Rate (BER) levels.

Energy Efficiency Optimization for Relay Deployment in Multi-User LTE-Advanced Networks

This paper proposes an energy-efficient position of relay node (RN) for a cooperative single amplify-and-forward relay. The optimum position of RN based on a single carrier-frequency division multiple access of LTE-A network is proposed. The proposed scheme models load balance to maximize energy efficiency (EE) for multiple users. Two categories of users (UEs) are considered; guaranteed bit rate (GBR) and non-guaranteed bit rate. The optimal position of RN is achieved to maximize the average EE for single-relay and total EE by satisfying all UEs. Additionally, the load distribution index in the cell is calculated when multiple RNs are considered. The simulation results have demonstrated that the proposed GBR achieves the objective value in terms of total and average EE by balancing load. Therefore, it is concluded that the optimum position of RN is at 74.5% of the cell radius.

Hardware co simulation of LTE physical layer for mobile network applications

Due to the rapid growth of wireless technology, it has become possible to provide solutions for fading, interference, and multipath. Long term evolution and Long term evolution — Advanced systems describe the standards based on 3rd Generation partnership project to overcome issues related to wireless technology. These techniques mitigate the latency and improves the system capacity. The Long term evolution physical layer uses orthogonal frequency division multiple access for downlink, and Single carrier-frequency division multiple access for uplink. Therefore this study provides a comprehensive investigation of orthogonal frequency division multiple access and Single carrier-frequency division multiple access transmission model and investigate physical layer performance of Long term evolution system using MATLAB – Simulink – Xilinx system generator platform based on releases, simulation implementation; results may be discussed in terms of Register transfer level design, power estimation, and resource estimation. For synthesis and implementation of the above architecture Plan ahead tool on Virtex, device board is used. • Due to the rapid growth of wireless technology it is necessary to provide the solutions for fading, interference and multipath. • Long Term Evolution (LTE) and LTE Advanced techniques describes the 3GPP standards to overcome the issues and improves the capacity. • This paper proposes a model-based design using Simulink-Xilinx System Generator to demonstrate the physical layer characteristics. • After the analysis the design is ported on an FPGA platform directly from Simulink. • A hardware-in-loop simulation is done to study the device utilization, power consumption and processing time.

Flexible Multi-Group Single-Carrier Modulation: Subcarrier Mapping and Power Allocation Optimization

Orthogonal frequency-division multiplexing (OFDM) and single-carrier frequency-domain equalization (SC-FDE) are the two commonly adopted modulation schemes for frequency-selective channels. Compared to SC-FDE, OFDM generally achieves higher data rates but at the cost of higher transmit signal peak-to-average power ratio (PAPR), which leads to lower power-amplifier efficiency. This paper studies a multi-group single carrier modulation scheme, termed flexible multi-group single carrier (FMG-SC), which encapsulates both OFDM and SC-FDE as special cases, thus achieving more flexible rate-PAPR tradeoffs between them. Specifically, in FMG-SC, the total bandwidth is divided into a set of orthogonal subcarriers that, based on the channel gains, are flexibly mapped to multiple non-overlapping groups, and SC-FDE is applied over each group independently to send multiple data streams in parallel. We investigate the joint subcarrier grouping and power allocation optimization problem to maximize the achievable rate of our proposed FMG-SC scheme for both the cases with Gaussian signaling and with practical modulation constellation (e.g., quadrature amplitude modulation), respectively. For both cases, the optimization problem is non-convex in general, for which we propose a two-step approach for finding a high-quality approximate solution efficiently. First, with any given subcarrier grouping, we show that the optimal power allocation can be obtained via convex optimization techniques. Second, with fixed power allocation, we propose low-complexity algorithms for the subcarrier grouping design catering to the SC-FDE receiver. Numerical results show that our proposed algorithms perform close to the optimal solution obtained via exhaustive search over all subcarrier groupings yet with substantially reduced complexity. Moreover, the achievable rate of our proposed FMG-SC scheme with Gaussian signaling approaches the OFDM channel capacity and significantly outperforms that of SC-FDE. Furthermore, with practical modulation constellation, numerical results show that our proposed FMG-SC scheme greatly outperforms the existing single carrier frequency-division multiple access in terms of achievable rate but with moderately increased PAPR.

Distributed Polar Coded Single Carrier-FDMA Based on Multilevel Construction Over Multipath Channels

A multilevel constructed polar coded single carrier frequency division multiple access (MLPC-SCFDMA) scheme is proposed and its bit-error rate performance over the multipath channels is examined. The multilevel construction of the polar code effectively divides the larger length polar code into two smaller length polar codes. This effective division of the polar codes have motivated the authors to efficiently transform the proposed scheme into coded-cooperative communication scheme. The relay’s contribution has always been given a supreme importance in the design of the any coded-cooperative communication system. Therefore, the authors have employed the use of re-transmission of the bad bit channels at the relay node. Moreover, in order to validate and compare its bit-error rate performance, the authors have also devised existing nested polar coded cooperative (NPCC) SCFDMA scheme over multipath channels. Numerical results based on Monte Carlo simulations demonstrate the superiority of multilevel constructed polar coded-cooperative SCFDMA scheme over traditional NPCC-SCFDMA scheme by gain of 0.2–0.3 dBs under similar conditions. This evident improved bit-error rate performance has occurred mainly because of an efficient re-transmission of the bad bit channels by polar sub-code placed at the relay node and the joint successive cancellation polar decoder efficiently utilized at the destination node. Moreover, the proposed multilevel constructed polar coded-cooperative SCFDMA scheme outperforms its corresponding multilevel polar coded SCFDMA (non-cooperative) scheme by the margin of 0.4 dBs under similar conditions.

Joint Clustering of Users and Resources for Multi-Cell VMIMO-SC-FDMA Uplink Systems

In this paper, we investigate the joint clustering of users and resources based on minimum mean square error-ordered successive interference cancellation (MMSE-OSIC) equalization for multi-cell single carrier-frequency division multiple access (SC-FDMA) uplink systems. To exploit the properties of the MMSE-OSIC equalization, we formulate the dynamic user grouping and resource allocation as a clustering problem, where resources are divided into several clusters and users are assigned into different clusters. Furthermore, we develop a new efficient K-means type algorithm named iterative K-groups clustering algorithm (IKG_OSIC) to solve the optimization problem. By making use of the MMSE-OSIC results, IKG_OSIC algorithm largely reduces the computation complexity of the joint resource allocation problem. The simulation results show that the proposed algorithm achieves good tradeoff between the performance and complexity and has better system throughput than the existing algorithms for virtual multiple-input multiple-output single carrier-frequency division multiple access (VMIMO-SC-FDMA) uplink systems.

Security-Enhanced SC-FDMA Transmissions Using Temporal Artificial-Noise and Secret Key Aided Schemes

We investigate the physical-layer security of uplink single-carrier frequency-division multiple-access (SC-FDMA) systems. Multiple users, Alices, send confidential messages to a common legitimate base-station, Bob, in the presence of an eavesdropper, Eve. To secure the legitimate transmissions, each user superimposes an artificial noise (AN) signal on the time-domain SC-FDMA data symbol. We reduce the computational and storage requirements at Bob's receiver by assuming simple per-sub-channel detectors. We assume that Eve has global channel knowledge of all links in addition to high computational capabilities, where she adopts high-complexity detectors such as single-user maximum likelihood (ML), multi-user minimum-mean-square-error, and multi-user ML. We analyze the correlation properties of the time-domain AN signal and illustrate how Eve can exploit them to reduce the AN effects. We prove that the number of useful AN streams that can degrade Eve's signal-to-noise ratio is dependent on the channel memories of Alices-Bob and Alices-Eve links. Furthermore, we enhance the system security for the case of partial Alices-Bob channel knowledge at Eve, where Eve only knows the precoding matrices of the data and AN signals instead of knowing the entire Alices-Bob channel matrices, and propose a hybrid security scheme that integrates temporal AN with channel-based secret key extraction.

A New Method to Enhance SC-FDMA Communication with Channel Estimation Errors

The single-carrier frequency division multiple access (SC-FDMA) system is a popular system in mobile communication because of its advantage of low peak-to-average-power-ratio (PAPR), and the use of frequency-domain equalizers to reduce inter-symbol interference (ISI) and inter-carrier interference (ICI). This paper presents a comprehensive study of the SC-FDMA system with PAPR reduction using clipping and filtering in the presence of channel estimation errors for two different versions of SC-FDMA adopting the FFT and the DCT. The effect of peak power reduction and the channel estimation error on the system bit error rate (BER) is investigated. Simulation results prove that the BER performance is not much affected by the PAPR reduction.

Generalized Discrete Fourier Transform for FBMC Peak to Average Power Ratio Reduction

Filter bank multicarrier (FBMC) is a strong candidate as a waveform based technique in advanced wireless communication systems (e.g. 5G), as an alternative to orthogonal frequency division multiplexing (OFDM). Like all multicarrier modulation techniques, FBMC suffers from high levels of a peak-to-average power ratio (PAPR). Discrete Fourier transform (DFT) spreading can be used in FBMC for PAPR reduction with a quite notable increase in computational complexity and without any need for side information (SI) overhead at the receiver. However, the achieved PAPR reduction is of a marginal amount, compared to the single carrier effect in the single carrier frequency division multiple access (SC-FDMA). This is due to the in-phase and quadrature phase (IQ) overlapping structure between offset quadrature amplitude modulation (OQAM) FBMC symbols. In this paper, we propose the use of generalized DFT (GDFT) spreading as an alternative to DFT spreading for PAPR reduction in systems employing FBMC. We derive the conditions at which the GDFT can totally make use of the single carrier effect of DFT spreading and hence reducing the PAPR. We also propose an enhancement algorithm that is utilized in the GDFT for further PAPR reduction without any additional complexity overhead. From the simulation results that are run at different values of subcarriers, it is shown that the GDFT spreading with the enhancement algorithm (enhanced GDFT) attain an extra amount of PAPR reduction over the other DFT spreading techniques. In addition, the GDFT spreading technique and the enhanced one also show better power spectral density (PSD) over the other DFT spreading techniques.

Open Loop and Closed Loop Power Control Analysis on LTE

LTE downlink is using Orthogonal Frequency Division Multiple Access (OFDMA) multiple access system which have high invulnerability from multipath problem. One of the weakness of OFDM system is the high level from Peak to Average Power Ratio (PAPR) that was required higher level transmit power for maintaining the Bit Error Rate (BER) requirement. Using uplink scheme with Single Carrier FDMA (SC-FDMA) which is OFDMA modification, will be offered better level of PAPR than its conventional OFDM. The main problem of using OFDMA is the high level of PAPR, while using SC-FDMA the problem is intra-cell interference. Intra-cell or inter-cell interference is the common problem that can reduce the LTE performance. Minimizing received power for each users (UE) which is still at acceptable tolerance parameter, can be used for reducing the interference problem to another UE. Power control is the appropriate solution for minimizing the interference level. In this paper will be analyzed the power control using open loop and closed loop scheme at LTE network. The simulation result show that without power control schemes, the transmit power of UE is 23 dBm. While, after applying power control scheme, the transmit power is 18.8 dBm at ?=0.4 of open loop condition and 9.05 dBm at closed loop condition. Using this transmit power value as the UE power can improve the SINR performance. The SINR average value without power control scheme is only 20.38 dB which is lower than using open loop scheme is achieved 22.44 dB and 24.02 dB at closed loop scheme.

Pruned DFT-Spread FBMC: Low PAPR, Low Latency, High Spectral Efficiency

We propose a novel modulation scheme which combines the advantages of filter bank multi-carrier (FBMC)-offset quadrature amplitude modulation and single-carrier frequency-division multiple access (SC-FDMA). On the top of a conventional FBMC system, we develop a novel precoding method based on a pruned discrete Fourier transform (DFT) in combination with one-tap scaling. The proposed technique has the same peak-to-average power ratio as SC-FDMA but does not require a cyclic prefix and has much lower out-of-band emissions. Furthermore, our method restores complex orthogonality, and the ramp-up and ramp-down period of FBMC is dramatically decreased, allowing low latency transmissions. Compared to pure SC-FDMA, the computational complexity of our scheme is only two times higher. Simulations over doubly selective channels validate our claims, further supported by a downloadable MATLAB code. Note that pruned DFT-spread FBMC can equivalently be interpreted as a modified SC-FDMA transmission scheme. In particular, the requirements on the prototype filter are less strict than in conventional FBMC systems.

A Novel ANN Equalizer to Mitigate Nonlinear Interference in Analog-RoF Mobile Fronthaul

We first analyze the nonlinearities in the analog radio-over-fiber (A-RoF)-based mobile fronthaul systems with a multi-user uplink load. The inter-band cross modulations (XMs) present in the common fiber channel cause severe inter-user interference. Then, we propose a novel complex-valued multi-level artificial neural network nonlinear equalizer (ANN-NLE) for single-carrier frequency division multiple access signal uplink transmissions. The inter-user interference can be mitigated by employing a multi-user ANN-NLE. Finally, we design an experimental test bed comprising a 60-GHz wireless link and an A-RoF link in order to verify the model predictions and thereby demonstrate the ability of the ANN-NLE to overcome the nonlinear intra-band and inter-band XMs in the case of simultaneous joint equalizations of all users (multi-point-to-single-point) as well as in the case of individual user equalizations (point-to-point). From the experimental and simulation results, we demonstrate that the ANN-NLE can substantially reduce the inter-user interference and communication bit error.