Search Radius Setting and Updation for Sphere Decoder for MIMO systems

Multiple Input Multiple output Orthogonal Frequency division Multiplexing (MIMO-OFDM) is a prepossessing modulation technique that have achieve notable heed in wireless environment nowadays. It improves the bandwidth efficiency and increases system capacity so as to provide a reliable transmission. However it has a high increase in PAPR (peak-to-average power ratio) due to the use of large number of sub carriers which result in many restrictions for practical applications. A novel hybrid approach is presented in this paper for the PAPR reduction by merging PTS and clipping together. This paper consists of various technique for reducing peak-to-average power ratio that are developed in last two decades such as PTS, clipping, CMA etc. The simulation result shows a collation between different PAPR reduction techniques. We propose and demonstrate an algorithm using two different techniques together and the results are verified using MATLAB software. We also comment on the computational complexity and practicability of these approaches.

We propose an algorithm to reject co-channel interference in 3GPP long term evolution (LTE) multiple input multiple output orthogonal frequency division multiplexing (MIMO- OFDM) systems. An improved channel estimation method and interference rejection algorithm are discussed. The interference information is measured on the pilot sub-carriers which are sent regularly in time and frequency. An improved model averaged interference mitigation method parameterizes the interference and noise spatial-covariance-matrix on each carrier as a combination of several low-rank models, each associated with probability soft information. A reduced complexity a posteriori receiver is derived based on the low-rank spatial covariance model. Parameterizing the interference and noise covariance matrix helps in adapting receiver for different interference scenarios. Simulation results are provided to demonstrate the efficacy of the model averaged interference rejection method applied to MIMO-OFDM system.

This Paper is containing the different types of Channel Coding which is used in multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM). To increase the efficiency of MIMO-OFDM there are several channel coding are applied in it.in this paper the aim is to show the discussion about all channel coding which are used as well as using in MIMO-OFDM system. This paper is structured in such way that in section I OFDM System and channel coding is described, in II section there is discussion about block diagram.In III section there is discussion of formula used in FFT and IFFT. In section IV several channel coding are defined which are used in MIMO-OFDM system. Further conclusion is made in section V.

In this paper, a model of space-frequency block coded multiple input multiple output orthogonal frequency division multiplexing (SFBC MIMO-OFDM) system is presented. The BER performance of this system is investigated for correlated MIMO channels. The analysis includes channel estimation errors.

In the past decades, researchers/scientists have paid attention to the physical layer of underwater communications (UWCs) due to a variety of scientific, military, and civil tasks completed beneath water. This includes numerous activities critical for communication, such as survey and monitoring of oceans, rescue, and response to disasters under the sea. Till the end of the last decade, many review articles addressing the history and survey of UWC have been published which were mostly focused on underwater sensor networks (UWSN), routing protocols, and underwater optical communication (UWOC). This paper provides an overview of underwater acoustic (UWA) physical layer techniques including cyclic prefix orthogonal frequency division multiplexing (CP-OFDM), zero padding orthogonal frequency division multiplexing (ZP-OFDM), time-domain synchronization orthogonal frequency division multiplexing (TDS-OFDM), multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM), generalized frequency division multiplexing (GFDM), unfiltered orthogonal frequency division multiplexing (UF-OFDM), continuous phase modulation orthogonal frequency division multiplexing (CPM-OFDM), filter bank multicarrier (FBMC) modulation, MIMO, spatial modulation technologies (SMTs), and orthogonal frequency division multiplexing index modulation (OFDM-IM). Additionally, this paper provides a comprehensive review of UWA channel modeling problems and challenges, such as transmission loss, propagation delay, signal-to-noise ratio (SNR) and distance, multipath effect, ambient noise effect, delay spread, Doppler effect modeling, Doppler shift estimation. Further, modern technologies of the physical layer of UWC have been discussed. This study also discusses the different modulation technology in terms of spectral efficiency, computational complexity, date rate, bit error rate (BER), and energy efficiency along with their merits and demerits.

In this paper, we propose an optimal power allocation scheme for joint pilot placement and space frequency (SF) code design for multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) wireless channels. OFDM is combined with multiple antennas to increase data diversity gain on a time varying multipath fading channel, resulting in a MIMO-OFDM system. A set of fast time-varying and frequency-selective fading channels is considered. The proposed pilot assisted transmission scheme multiplexes known symbols with information bearing data to estimate the channel in the presence of inter symbol interference (ISI). The channel is assumed to be unchanged for the duration of one OFDM block and change independently from one OFDM block to the other. The number of pilot symbols for each OFDM block is held constant and the symbols are dispersed throughout the block for efficient channel estimation. However, equally distributing the total power between the data and pilots doesn't optimize the transmission over a frequency-selective fading channel. We propose an optimal power allocation scheme for the joint pilot placement and space frequency code design scheme based on the channel response and the bit error rate (BER) values. This leads to substantial improvement in performance for a 2 times 2 MIMO-OFDM system. The results can be extended to MIMO-OFDM systems with any number of transmit and receive antennas.

本論文では，Ricianチャネルにおける過負荷Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM)システムに対してターボ符号と位相プレコーディング係数を導入した場合の効果を検討する．誤り訂正符号を用いた過負荷MIMO-OFDMでは，マルチパスによる周波数ダイバーシチによって信号ストリームの空間多重による特性劣化を抑えている．しかし，見通し内環境ではLine-of-sight成分が支配的となるため，符号語毎の信号ストリーム間の相関が高くなり，誤り率特性の劣化を引き起こす．本研究では相関低減のため，OFDMシンボル毎に位相プレコーディング係数を導入する．計算機シミュレーションおよび実験の結果，提案方式はプレコーディングを適用しない場合に比べて10-3で約0.5～1.5dB特性を改善した．

In this paper, we propose a receiver architecture that can demodulate multiple data streams with different frequency offsets and propagation delays in multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) ad hoc networks. The receiver performs joint synchronization and interference cancellation to separate these interfering data streams and achieve synchronization for each stream. We propose a novel training-based minimizing mean square error (MMSE) algorithm to jointly obtain the frequency offsets and the equalization delays. The effects of frequency offsets and propagation delays are compensated with these estimated parameters. We also propose a direct training-based equalizer design algorithm to obtain the equalizer coefficients. This algorithm involves solving an optimization problem that considers symbol error rate. Simulation shows good uncoded bit error rate performance for our proposed algorithms.

Three dimensional discrete element simulation of cylindrical cavity expansion from zero initial radius in sand

Timing synchronization using cross ambiguity function for MIMO OFDM systems with distributed antennas

Optical communication system for the next generation of wireless communication systems are an exciting, unparalleled new technology. This paper presents a new visible light positioning algorithm system based on position by utilized neural network, which depending on directly measured received signal strength (RSS) information of 3D coordinates. This algorithm is called light positioning algorithm neural network (LPANN) which used 5 laser diodes LDs, each one consists of 5×5 LD chips. In addition, a novel multi Input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) based VLC systems generalized laser diodes (LD) modulation scheme as second part of this paper that is called Zero Forcing Equalizer Neural network ZFENN algorithm which based on 4 × 4 optical MIMO-VLC. It is accomplished by using LD index modulation and spatial multiplexing. Actual and imaginary parts of the complex time domain OFDM signals are therefore separated first and then, bipolar signals are transmitted through VLC channels by encoding sign-information in LD indexes. In addition, a novel receiver configuration is also suggested for flat frequency or limited channel scenarios. Based on the results of this analysis, the positioning accuracy have been improved, so this is lead to enhance data rate. While, by using the second part of the MIMO-OFDM system that leads to enhancing the SNR and BER more than 10-4, which are introduced to eliminate multi-user interference (MUI).

This paper proposes a new hybrid cyclic delay diversity (HCDD) scheme for multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. Unlike the existing double space time transmit diversity (DSTTD) and stacked cyclic delay diversity (SCDD) schemes that are suitable for integer multiplexing rates, the proposed HCDD scheme can achieve arbitrary non-integer multiplexing rates. Our results demonstrate that the HCDD scheme can provide flexibility in selecting the required number of transmitting antennas and in adjusting diversity and multiplexing gains to match various users requirements. The advantages of the proposed HCDD, including the flexible rate assignment and less complex receivers, are presented in applications of scalable video broadcasting (SVB).

Free Space Optical (FSO) communication is an emerging technology to provide high bandwidth, secure and high quality communication. In this work we have determined the capacity of the Free Space Optical communication system with Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) technique under weak atmospheric turbulence conditions. To model the weak turbulence condition of the atmosphere lognormal channel model is used throughout the work. The capacity of MIMO-OFDM FSO is evaluated in the presence of Inter Symbol Interference (ISI) and is compared with MIMO FSO with ISI. The capacity of MIMO-OFDM FSO system increases in comparison to MIMO in the presence of ISI. It is found that the effect of ISI is mitigated by using OFDM and the capacity is enhanced. Since MIMO uses spatial divervity to mitigate the fading caused by turbulence hence the capacity of both MIMO-OFDM FSO and MIMO FSO also increases as the number of receiving antennas is increased.

I/Q imbalance, which is one of the radio frequency (RF) circuit impairments in direct conversion transmitter and receiver, introduces severe performance degradation in wireless communication systems. In this paper, we propose a novel blind compensation algorithm for both frequency-dependent and frequency-independent I/Q imbalance based on independent component analysis (ICA) in multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) systems, where ICA, an efficient higher order statistics (HOS) based blind source separation technique, is applied to compensate for I/Q imbalance and equalize the received signals simultaneously. Moreover, precoding is employed to resolve the ambiguity in the ICA output signals. Simulation results show that the proposed approach can not only compensate for I/Q imbalance effectively, but also achieve frequency diversity gains and outperform the case with perfect channel state information (CSI) and no I/Q imbalance.

In this paper, we present a pre-transformed (PT) multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) system, in short PT-MIMO-OFDM system. We propose two receiver structures that combine the iterative subcarrier reconstruction and iterative interference cancellation to fully exploit both the spatial and the frequency diversity of MIMO-OFDM systems. Significant performance gain can be achieved. Based on the performance and receiver complexity tradeoff, we also present a set of guidelines for choosing either one of the two receivers in practical systems