Orthogonal frequency division multiplexing

The contribution serves as a preview of the OFDM modulation signal, which is used in cellular and other wireless networks. We look closer on this problem and we are subsequently discussed general topics. That include an issue of mobile networks in their general concept and also more insight on the network 4 and 5 generations. Within the network 4 generations, namely LTE and LTE-A is approximated architecture and properties of these networks. In a 5-generation networks that reach into realization in the future, we have discussed concepts of architecture and other features. © Research India Publications

ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING

ABSTRACT Orthogonal frequency division multiplexing (OFDM) is a method of modulation of digital signal i

OFDM: A Mathematical Review

Mathematical review of the Orthogonal Frequency Division Multiplexing is demonstrated in terms of Inter symbol interference, Multi carrier modulated system and cyclic prefix. Modeling of the mathematical equation of the Orthogonal Frequency Division Multiplexing, Inverse fast Fourier transform and fast Fourier transform is explained with the suitable example using MATLAB. Bit error rate performance of OFDM is also presented with the help of statistical computation

Weyl-Heisenberg Spaces for Robust Orthogonal Frequency Division Multiplexing

Design of Weyl-Heisenberg sets of waveforms for robust orthogonal frequency division multiplex- ing (OFDM) has been the subject of a considerable volume of work. In this paper, a complete parameterization of orthogonal Weyl-Heisenberg sets and their corresponding biorthogonal sets is given. Several examples of Weyl-Heisenberg sets designed using this parameterization are pre- sented, which in simulations show a high potential for enabling OFDM robust to frequency offset, timing mismatch, and narrow-band interference

ANALISIS KINERJA ALGORITMA ADAPTIVE BEAMFORMING PADA SISTEM ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING (OFDM) Performance Analysis of Adaptive Beamforming Algorithm on Orthogonal Frequency Division Multiplexing (OFDM) System

ABSTRAKSI: Seiring dengan meningkatnya permintaan layanan dengan laju data tinggi akan berdampak pada penggunaan bandwidth yang sangat lebar. Dalam kasus ini, kanal akan bersifat frequency-selective, yang akan menyebabkan munculnya multipath fading yang akan menyebabkan distorsi. Orthogonal Frequency Division Multipexing (OFDM) merupakan skema komunikasi multicarrier dimana bandwidth kanal dibagi menjadi beberapa subcarrier dan simbol data dimodulasi dan ditransmisikan pada tiap subcarrier. OFDM sangat efektif digunakan untuk mengatasi distorsi akibat multipath. Sistem OFDM juga dapat mengatasi Intersymbol Interference (ISI), dengan menyisipkan guard time yang lebih lebar daripada delay spread kanal. Penerapan sistem OFDM yang sudah cukup baik menangani interferensi dapat ditingkatkan kinerjanya dengan menerapkan Adaptive Array Antenna. Penerapan Adaptive Array Antenna yang menggunakan beberapa elemen antena untuk beamforming, akan membantu untuk memisahkan sinyal yang diinginkan dari sinyal penginterferensi.Penelitian dilakukan untuk meneliti penerapan adaptive array antenna pada sistem OFDM dan menganalisa kinerja sistem dalam lingkungan fading. Algoritma adaptif yang digunakan dalam penelitian adalah algoritma Least-Mean Square (LMS) dan algoritma Recursive Least-Square (RLS). Selain itu akan dianalisa kinerja sistem dengan beamforming jika menggunakan dua, empat dan delapan elemen antena pada receiver. Kemudian diperhitungkan pula pengaruh dari kecepatan user terhadap kinerja sistem.Hasil simulasi membuktikan bahwa penerapan adaptive array antenna pada sistem OFDM dapat meningkatkan kinerja sistem OFDM sehingga dapat mengatasi interferensi dengan lebih baik. Tetapi kecepatan user yang tinggi dapat menurunkan kinerja dari sistem.Kata Kunci : ABSTRACT: As the demand of high data rate services increased, wide bandwidth is needed to accommodate it. In this case, the channel’s characteristic is frequency-selective which will cause multipath fading effect that can distort the signal. Orthogonal Division Multiplexing (OFDM) is a multicarrier communication scheme which divides channel bandwidth into several subcarrier, data symbol is modulated and transmitted in each subcarrier. OFDM is effective to handle distortion caused multipath effect. It can also handle Intersymbol Interference (ISI) by inserted guard time wider than the channel delay spread. An adaptive array antenna is implemented to improve the performance of OFDM system to handle interference. The adaptive array antenna implementation which uses some antenna elements for beamforming will help to separate wanted signal from the interferer.This final project research and analyze the implementation of adaptive array antenna on OFDM system and analyze the performance of the system in fading environment. The adaptive algorithms used in this final project are Least-Mean-Square (LMS) algorithm and Recursive Least-Square (RLS) algorithm. This final project will also analyze the performance of the system with beamforming using two, four and eight elements placed in receiver side. Furthermore, the effect of user’s velocity to the system’s performance will be analyzed too.Simulation result shows that the implementation of adaptive array antenna on OFDM system can increase its performance. More antenna elements used in the receiver will increased the system’s performance. But higher velocity of user, decrease its performance.Keyword

Soft-Information Assisted Near-Optimum Nonlinear Detection for BLAST-type Space Division Multiplexing OFDM Systems

In this contribution, a nonlinear hybrid detection scheme based on a novel soft-information assisted Genetic Algorithm (GA) is proposed for a Turbo Convolutional (TC) coded Space Division Multiplexing (SDM) aided Orthogonal Frequency Division Multiplexing (OFDM) system. Our numerical results show that the performance of the currently known GA-assisted system can be improved by about 2dB with the aid of the GA’s population-based soft solution, approaching the optimum performance of the soft-information assisted Maximum Likelihood (ML) detection, while exhibiting a lower complexity, especially in high-throughput scenarios. Furthermore, the proposed scheme is capable of achieving a good performance even in the so-called overloaded systems, where the number of transmit antennas is higher than the number of receiver antennas. Index Terms—Genetic algorithm, orthogonal frequency division multiplexing, soft information, space division multiplexing