SISO OFDM Research Articles

Theoretical Analysis of Adaptive Algorithm Modulation Scheme in 3D OFDM WiMAX System

The growth of wireless networking has contributed to the need for high-speed services and multimedia applications anywhere and at any time. OFDM WiMAX technology is now considered one of the most popular technologies capable of delivering faster implementation and lower cost than standard wired options for Broadband Wireless Connectivity in metropolitan areas. This paper proposes appropriate adaptive modulation to be used in wireless networks based on SISO and MIMO OFDM WiMAX, which allows the performance of the network to be improved in the case of non-line-of-sight communications that are typical in urban environments. The effects of several paths, signal attenuation, Doppler shift, and different mobility speeds on the performance of the system were investigated. Mathematical models analysis of adaptive modulation in SISO and MIMO systems is treated by using BER, SNR and noise components. Simulation results show that the adaptive algorithm would improve throughput. It can also be concluded that when processing signals in a receiving system under conditions of multi-path signal propagation, the use of adaptive algorithms has a positive effect on noise immunity.
 HIGHLIGHTS
 
 With the growing evolution of wireless communication technologies, there is still a need for higher data rates, increased system capacity, and improved service quality
 3D OFDM-MIMO WiMAX technology is now regarded as one of the most common solutions for Broadband Wireless Connectivity in Urban Areas, capable of offering faster implementation and lower costs than standard wired options
 Effective adaptive algorithm processing in 3D wireless networks based on SISO-OFDM and MIMO-OFDM WiMAX was proposed, enabling network performance to be enhanced in the case of non-LOS wireless communications, which are standard in urban conditions. On the performance of the system, signal attenuation, the effects of several paths, different mobility speeds and Doppler shift were studied
 The adaptive algorithm significantly reduces the probability of error and increases the throughput. It can be concluded that the use of adaptive spatio-temporal algorithms has a positive effect on noise immunity when processing signals in the receiving system under conditions of multipath signal propagation
 
 GRAPHICAL ABSTRACT

Transmitting Image in 3D Wireless Channel using Adaptive Algorithm Processing with MMSE based on MIMO principles

With the growing evolution of wireless communication technologies, there is still a need for higher data rates, increased system capacity, and improved service quality. OFDM WiMAX technology is now regarded as one of the most common solutions for Broadband Wireless Connectivity in Urban Areas, capable of offering faster implementation and lower costs than standard wired options. This paper proposes effective adaptive algorithm processing with MMSE for use in wireless networks based on SISO and MIMO OFDM WiMAX, enabling network performance to be enhanced in the case of non-LOS wireless communications, which are standard in urban conditions. On the performance of the system, signal attenuation, the effects of several paths l, different mobility speeds and Doppler shift were studied. Combines the adaptive algorithm with MMSE, achieves improved joint channel estimation and signal detection which performs the technique effectively mobile. SNR, MSE and noise components are used to analyses mathematical models of adaptive modulation for transmitting images in SISO and MIMO systems. Simulation results show that the adaptive algorithm with MMSE would improve throughput. For example, when SNR equal 15 dB, the probability of MSE for BPSK based on MIMO principle is equal to 0.0016 with adaptive algorithm. Also, for the same value of SNR, the probability of MSE for BPSK based on MIMO principle is equal to 0.164 without adaptive algorithm. It can also be concluded that when processing signals in a receiving system under conditions of multi-path signal propagation, the use of adaptive algorithms with MMSE has a positive effect on noise immunity.

ML-Type EM-Based Estimation of Fast Time-Varying Frequency-Selective Channels Over SIMO OFDM Transmissions

This paper investigates the problem of fast time-varying frequency-selective (i.e., multipath) channel estimation over single-input multiple-output orthogonal frequency-division multiplexing (SIMO OFDM)-type transmissions. We do so by tracking the variations of each complex gain coefficient using a polynomial-in-time expansion. To that end, we derive the log-likelihood function (LLF) both in the data-aided (DA) and non-data-aided (NDA) cases. The DA maximum likelihood (ML) estimates over fast SIMO OFDM channels are derived here for the first time in closed-form expressions and hereby shown to be limited to applying over each receive antenna the DA least squares (LS) estimator tailored in [1] to fast SISO OFDM channels. This DA ML is used to initialize periodically, over a relatively large number of data blocks (i.e., with further reduced and relatively close-to-negligible pilot overhead compared to DA ML), a new expectation maximization (EM) ML-type solution we developed here in the NDA case to iteratively maximize the LLF. We also introduce an alternative regularized DA ML (RDM) initialization solution no longer requesting - in contrast to DA ML - more per-carrier pilot frames than the number of paths to further reduce overhead without incurring significant performance losses. Simulation results show that the proposed hybrid ML-EM estimator (i.e., combines all new NDA ML-EM and DA ML or RDM versions) converges within few iterations, thereby providing very accurate estimates of all multipath channel gains. Most importantly, this increased estimation accuracy translates into very significant BER and link-level per-carrier throughput gains over the best representative benchmark solution available so far for the problem at hand, the SISO DA LS technique in [1] with its new generalization here to SIMO systems.

Implementasi Sistem Komunikasi Nirkabel OFDM Berbasis Software Defined Radio (SDR)

Nowadays, wireless communication technology is developing rapidly. However, this technology still has some weaknesses, e.g. large bandwidth requirement and multipath fading. To overcome these weaknesses, MIMO OFDM technique is needed. This paper implements MIMO OFDM 2x2 communication system in Universal Software Radio Peripheral (USRP). The performance of MIMO OFDM 2x2 is shown by the throughput value. This value is compared to the throughput value of single carrier and SISO OFDM. The modulations used are BPSK, 4-QAM, and 16-QAM. In 4-QAM modulation, the throughput value of MIMO OFDM is significantly larger than throughput value of single carrier and SISO OFDM. The throughput value of single carrier communication system is 27.71 Mbit/s, while the throughput value of the SISO OFDM communication system is 60.27 Mbit/s, and the throughput value of the MIMO OFDM 2x2 communication system is 123.03 Mbit/s.

Retraction notice to: “Adaptive algorithm for wireless data transmission (including images) based on SISO system and OFDM technique”

At the request of the Authors, the following article has been retracted from MATEC Web of Conferences Volume 226 for the following reason: This article was sent simultaneously by mistake to two different journals, MATEC Web of Conferences and another journal, generating an ethical problem of double publication. The organizers and the authors apologize for the mistake that is more related to an administrative error than a deliberate misconduct. The Editorial Board of MATEC Web of Conferences and EDP Sciences have agreed to retract the article. Refers to RETRACTED: Adaptive algorithm for wireless data transmission (including images) based on SISO system and OFDM technique, Valentin Fedosov, Andrey Legin and Anna Lomakina, published online on 07 November 2018

Adaptive algorithm for wireless data transmission (including images) based on SISO system and OFDM technique

The efficiency of wireless systems to transmit information in a complex interference situation is one of the main indicators of the effectiveness of the system, which can be characterized by the probability of an error in the transmitted message. This characteristic depends on the interference situation of the communication channel and the nature of the signals propagation in the medium. If the medium has a multi-path character, the signal interferes with the receiving antenna, causing signal fading. So the developer of wireless communication devices is faced with the task of increasing the noise immunity of the system. It can be increased in various ways, for example, by using adaptive processing algorithms for spatio-temporal signals. In this paper we solve the problem of improving noise immunity in wireless communication systems by applying an algorithm of adaptive spatial-temporal signal processing in the receiver based on an adaptive antenna array, which allows spatial filtering under conditions of a complex pattern of signal propagation in a channel with reflections. Calculation of weights for the adaptation algorithm in the article is based on the theory of eigenvalues and vectors of the spatial correlation matrix.

RETRACTED: Adaptive algorithm for wireless data transmission (including images) based on SISO system and OFDM technique

RETRACTED: Adaptive algorithm for wireless data transmission (including images) based on SISO system and OFDM technique

Channel Estimation methods with low complexity for 3GPP/LTE

OFDM based pilots channel estimation methods with processing into the transform domain appear attractive owing to their capacity to highly reduce the noise component effect. However, in current OFDM systems, null subcarriers are placed at the edge of the spectrum in order to assure isolation from interfering signals in neighboring frequency bands; and the presence of these null carriers may lead, if not taken into account, to serious degradation of the estimated channel responses due to the “border effect” phenomenon. In this paper an improved algorithm based on truncated SVD is proposed in order to correctly support the case of null carriers at border spectrum. A method for optimizing the truncation threshold whatever the system parameters is also proposed. To make the truncated SVD channel estimation method applicable to any SISO or MIMO OFDM system and whatever the system parameters, a complexity reduction algorithm based on the distribution of the power in the transfer matrix (based on DFT or DCT) is proposed. Les techniques d’estimation de canal, basée sur des symboles pilotes, par passage dansun domaine de tranfert sont très attractives pour les systèmes de télécommunications utilisant l’OFDM.Cependant, elles montrent des limites pour les systèmes de télécommunications, où un ensemble desous-porteuses de garde, est inséré sur les bords du spectre dans le but d’éviter tout recouvrementspectral avec d’autres applications utilisant des bandes voisines. Ces sous-porteuses de gardeont selon leur nombre tendance à dégrader fortement les performances de ces estimateurs. Nousproposons, dans un premier temps, une optimisation qui permet d’améliorer considérablement lesperformances de ces estimateurs quels que soit le nombre de porteuses de garde. Dans un secondtemps, pour de rendre l’estimateur proposé attractif pour les constructeurs, nous avons proposé unetechnique permettant de réduire leur complexité de réalisation de manière notable.