Orthogonal Frequency Division Multiple Systems Research Articles

Enhanced optimization assisted interference mitigation with vertical beamforming in 3D MIMO-OFDMA for 5G wireless communication network

PurposeMultiple input multiple-output (MIMO) has emerged as one among the many noteworthy technologies in recent wireless applications because of its powerful ability to improve bandwidth efficiency and performance, i.e. through developing its unique spatial multiplexing capability and spatial diversity gain. For carrying out an enhanced communication in next-generation networks, the MIMO and orthogonal frequency division multiple systems were combined that facilitate the spatial multiplexing on resource blocks (RBs) based on time-frequency. This paper aims to propose a novel approach for maximizing the throughput of cell-edge users and cell-center users.Design/methodology/approachIn this work, the specified multi-objective function is defined as the single objective function, which is solved by the introduction of a new improved algorithm as well. This optimization problem can be resolved by the fine-tuning of certain parameters such as assigned power for RB, cell-center user, cell-edge user and RB allocation. The fine-tuning of parameters is attained by a new improved Lion algorithm (LA), termed as Lion with new cub generation (LA-NCG) model. Finally, the betterment of the presented approach is validated over the existing models in terms of signal to interference plus noise ratio, throughput and so on.FindingsOn examining the outputs, the adopted LA-NCG model for 4BS was 66.67%, 66.67% and 20% superior to existing joint processing coordinated multiple point-based dual decomposition method (JC-DDM), fractional programming (FP) and LA models. In addition, the throughput of conventional JC-DDM, FP and LA models lie at a range of 10, 45 and 35, respectively, at the 100th iteration. However, the presented LA-NCG scheme accomplishes a higher throughput of 58. Similarly, the throughput of the adopted scheme observed for 8BS was 59.68%, 44.19% and 9.68% superior to existing JC-DDM, FP and LA models. Thus, the enhancement of the adopted LA-NCG model has been validated effectively from the attained outcomes.Originality/valueThis paper adopts the latest optimization algorithm called LA-NCG to establish a novel approach for maximizing the throughput of cell-edge users and cell-center users. This is the first that work uses LA-NCG-based optimization that assists in fine-tuning certain parameters such as assigned power for RB, cell-center user, cell-edge user and RB allocation.

Enhanced spectrum sensing using a combination of energy detector, matched filter and cyclic prefix

In this paper, we propose a sensing scheme based on energy detection, matched filter and cyclic prefix. Both Equal Gain Combining (EGC) and optimal combination of the aforementioned detectors are investigated in cooperative and non-cooperative spectrum sensing scenarios. In packet transmission systems such as OFDM (Orthogonal Frequency Division Multiple access) systems, the proposed scheme takes advantage of utilizing more samples than individual detectors, i.e., cyclic prefix, training or pilot samples, and data payload samples. The proposed combine-sensing scheme offers higher detection probability and lower false alarm probability, as compared with the performance of individual detectors over the same frame duration. Simulation results are congruent with the theoretical curves and confirm the validity of our derivations.

New Iterative Method for Estimation of Carrier Frequency in Multicarrier Systems

The key problem for OFDM (Orthogonal Frequency Division Multiple) systems is who to Estimate carrier frequency offset (CFO) with reduced complexity and acceptable performance. The CFO must be compensated before DFT (Discrete Fourier Transform) in order to restore data correctly and enhance the system performance. This paper, present a low complexity estimator of CFO with Semi-Blind (SB) criterion based on pilot tones and on virtual subcarriers, and with the aid of subspace based method. However, MUSIC and ESPRIT based semi-blind algorithms require a highly computational complexity. To overcome this drawback, we use Taylor’s series for the first order as developed in [1]. The present methods developed in this paper are very suitable for Multi- Carrier (MC) systems when the CFO are present. Simulation results demonstrated that the semi-blind (SB) approach outperforms the blind-based approach.

Outage Minimized Resource Allocation for Multiuser OFDM Systems With SWIPT

This paper considers a downlink multiuser orthogonal frequency division multiple (OFDM) system with simultaneous wireless information and power transfer (SWIPT), where the users decode information and harvest energy using the same received downlink signals. In particular, both power splitting (PS) and time switching (TS) SWIPT modes are considered for coordinating information transferring and energy harvesting. For multiuser information transmission, OFDM access (OFDMA) and time division multiple access (TDMA) are adopted for PS-SWIPT and TS-SWIPT, respectively. The outage performance of such a multiuser OFDM system with SWIPT is investigated. Particularly, we optimize the subcarrier allocation, power allocation and PS ratio for PS-SWIPT, and the power allocation and time allocation for TS-SWIPT, aiming at minimizing the fraction of outage over all users under the minimum harvest energy constraint along with the peak and total transmit power constraints. Suboptimal heuristic algorithms are obtained based on the Lagrange duality method. The outage performances of PS-SWIPT and TS-SWIPT are compared under various system parameter settings. We show that the outage performance of TS-SWIPT is better than that of the PS-SWIPT, except when the minimum required harvested energy is large, the total transmit power limit is small, or the number of users is small.

Optimum power allocation in OFDM systems under power amplifier nonlinearity

In this paper, the optimum power allocation for subcarriers in orthogonal frequency division multiple system is derived which maximizes the total rate of system under nonlinearity of practical power amplifier. The rate of system by using analytical signal to interference ratio formula is optimized to derive optimal power scales for subcarriers. The problem is nonconvex and a comprehensive learning particle swarm optimization method is designed to solve the problem. The simulation results demonstrate that by considering nonlinearity in power allocation, better rate can be achieved compared to conventional power allocation methods.

Optimization of wireless information and power transfer in multiuser OFDM systems

Simultaneous wireless information and power transfer (SWIPT), which belongs to energy harvesting techniques, is an important research topic. In existing literature, two SWIPT schemes, namely the time switching (TS) scheme and the power splitting (PS) scheme are adopted. For multiuser orthogonal frequency division multiple (OFDM) systems, this paper proposes a new SWIPT scheme named as the subcarrier sharing (SS) scheme. Resource allocation algorithms for the SS scheme are then proposed for maximizing the sum rate under the minimum harvested energy constraint. We show that the SS scheme outperforms the existing TS and the PS schemes.

Energy‐efficient resource allocation in multiuser OFDM systems with proportional rate constraints

An efficient resource allocation scheme is presented to maximise energy efficiency for multiuser orthogonal frequency division multiple systems with proportional rate constraints. For a determined subchannel assignment, an optimal energy-efficient power allocation algorithm has been derived through a bisection search method.