scholarly journals Bit Rate Optimization with MMSE Detector for Multicast LP-OFDM Systems

2012 ◽  
Vol 2012 ◽  
pp. 1-12
Author(s):  
Ali Maiga ◽  
Jean-Yves Baudais ◽  
Jean-François Hélard
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Minimum Mean Square Error ◽  
Ofdm Systems ◽  
Bit Rate ◽  
Zero Forcing ◽  
Resource Allocation Algorithm ◽  
Bit Loading ◽  
Multirate Multicast ◽  
Mmse Detector ◽  
Rate Optimization

We propose a new resource allocation algorithm with minimum mean square error (MMSE) detector for multicast linear precoded orthogonal frequency division multiplexing (LP-OFDM) systems. To increase the total multicast bit rate, this algorithm jointly uses the LP-OFDM modulation technique and an adaptation of the OFDM-based multicast approaches to exploit the transmission link diversities of users. The LP technique applied to multicast OFDM systems with zero forcing (ZF) detector has already proved its ability to increase the unirate multicast system bit rate in a power line communication (PLC) context. The new MMSE detector and the new related bit-loading algorithm are developed to enhance the ZF detector results. To improve both the bit rate and the fairness among multicast users, the utilization of the LP component in multirate multicast systems is then investigated. Simulations are run over indoor PLC channels, and it is shown that the proposed LP-based methods outperform the OFDM-based methods in terms of total bit rate and fairness index for both unirate and multirate multicast systems. Additionally, it is shown that the proposed bit-loading algorithm with MMSE detector outperforms the ZF detector and the OFDM-based receiver in terms of total multicast bit rate and fairness among users.

scholarly journals Performance Evaluation of OFDM System with Insufficient CP Using LMS Equalizer under Harsh Multipath Conditions

2019 ◽  
Vol 15 (2) ◽  
pp. 122-129
Author(s):  
Abolqassem Fakher ◽  
Falih Alnahwi ◽  
Majid Alwan
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
High Performance ◽  
Minimum Mean Square Error ◽  
Lms Algorithm ◽  
Mean Square ◽  
Least Mean Square ◽  
Ofdm System ◽  
Zero Forcing ◽  
Ofdm Signal ◽  
Multipath Signals

This paper presents an insufficient cyclic prefix (CP) Orthogonal Frequency Division Multiplexing (OFDM) system with equalizer whose coefficients are calculated using Least Mean Square (LMS) algorithm. The OFDM signal is passed through a channel with four multipath signals which cause the OFDM signal to be under high inter-symbol interference (ISI) and inter-carrier interference (ICI).8-QAM and 16-QAM digital modulation techniques are used to evaluate the performance of the proposed system. The simulation results have accentuated the high performance of the LMS equalizer via comparing its Bit Error Rate (BER) and constellation diagram with those of the Minimum Mean Square Error and Zero Forcing equalizers. Moreover, the results also reveal that the LMS equalizer provides BER performance close to that of the OFDM system with a hypothetical sufficient CP.

OPTIMAL TRAINING DESIGN FOR MIMO–OFDM SYSTEMS UNDER SPATIALLY CORRELATED DOUBLY SELECTIVE FADING CHANNELS

2007 ◽  
Vol 16 (05) ◽  
pp. 673-697
Author(s):  
QINGHAI YANG ◽  
KYUNG SUP KWAK
Keyword(s):  
Lower Bound ◽  
Water Level ◽  
Fading Channels ◽  
Orthogonal Frequency Division Multiplexing ◽  
Minimum Mean Square Error ◽  
Optimal Number ◽  
Ofdm Systems ◽  
Selective Fading ◽  
Spatially Correlated ◽  
Pilot Symbols

In this paper, we design an optimal training scheme for multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems under spatially correlated time- and frequency- (doubly) selective fading channels. We first develop the optimal pilot symbols and placement of pilot clusters with respect to the minimum mean square error (MMSE) of the linear channel estimate. We then derive the optimal power allocation for pilot symbols in a two-water-level way: by maximizing the averaged capacity lower bound, how much power to be allocated for training is determined subject to the global water level (or the constraint of total transmit power); subsequently, pouring power to the pilot symbols with an approximately optimal water-filling scheme subject to the local water level (or the constraint of assigned power for training). In addition, for a particular OFDM size, the optimal number of pilot clusters is derived by maximizing the capacity lower bound and by minimizing the channel estimate's MMSE.

A MMSE Channel Estimation Method in QC-LDPC Coded OFDM Systems

2014 ◽  
Vol 989-994 ◽  
pp. 3759-3762 ◽  
Author(s):  
Gulomjon Sangirov ◽  
Yong Qing Fu ◽  
Ye Fang
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Wireless Channels ◽  
Minimum Mean Square Error ◽  
Estimation Method ◽  
Coherent Detection ◽  
Estimation Methods ◽  
Ofdm Systems ◽  
Computationally Efficient ◽  
Coded Ofdm

An orthogonal frequency division multiplexing (OFDM) is one of the effective techniques used in wireless communications. In OFDM systems, channel impairments due to multipath dispersive wireless channels can cause deep fades in wireless channels. The OFDM receiver also requires an accurate and computationally efficient channel state information when coherent detection is involved. Therefore, it needs a good robust estimation method of the channel in wireless communication for OFDM systems. And one of these channel estimation methods is minimum mean square error (MMSE) channel estimation. MMSE channel estimation one most used method in OFDM systems. In this work we enhanced robustness of MMSE channel estimation by using it in base of quasi-cyclic low density parity check (QC-LDPC) coded OFDM system.

scholarly journals Wiener-based ICI cancellation schemes for OFDM systems over fading channels

2013 ◽  
Vol 10 (2) ◽  
pp. 877-896 ◽  
Author(s):  
Jyh-Horng Wen ◽  
Yung-Cheng Yao ◽  
Ying-Chih Kuo
Keyword(s):  
Fading Channels ◽  
Interference Cancellation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Intercarrier Interference ◽  
Ofdm Systems ◽  
Computation Complexity ◽  
Zero Forcing ◽  
Ofdm Signals ◽  
Ici Cancellation ◽  
Better Than

The subcarriers of orthogonal frequency division multiplexing (OFDM) systems may fail to keep orthogonal to each other under timevarying channels. The loss of orthogonality among the subcarriers will degrade the system performace, and this effect is named intercarrier interference (ICI). In this paper, a Wiener-based successive interference cancellation (SIC) scheme is proposed to detect the OFDM signals. It provides good ICI cancellation performance; however, it suffers large computation complexity. Therefore, a modified Wienerbased SIC scheme is further proposed to reduce the computation complexity. Simulation results show the performance of the Wienerbased SIC scheme is better than those of zero forcing, zero forcing plus SIC and original Wiener-based schemes. Furthermore, with the modified Wiener-based SIC scheme, the performance is still better than the others. Although the performace of the modified Wiener-based SIC scheme suffers little degradation compared to Wiener-based SIC scheme, the computation complexity can be dramatically reduced.

An Efficient Packet Scheduling and Resource Allocation Algorithm for Practical Multi-Layer Systems

2014 ◽  
Vol 926-930 ◽  
pp. 2951-2954
Author(s):  
Yue Huai Ma ◽  
Wei Zhang ◽  
Wen Hua Wang ◽  
Yue Xuan Liu
Keyword(s):  
Resource Allocation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Packet Scheduling ◽  
Hot Spot ◽  
Packet Delay ◽  
Physical Layer ◽  
Ofdm Systems ◽  
Mac Layer ◽  
Resource Allocation Algorithm ◽  
Wireless Resource Allocation

In this paper, we research the wireless resource allocation problem with packet scheduling in both MAC layer and physical layer in multi-user orthogonal frequency division multiplexing (OFDM) systems. Under the practical environment where mobile users receiving signal with different SNR levels in a cell or around a Wi-Fi hot spot, our designed algorithm can execute relatively fair packet scheduling from MAC layer consideration and make efficient use of wireless resources at physical layer. simulation results show that our proposed scheme satisfy most users in various SNR and have better average performance in packet drop rate, packet delay and total throughput.

scholarly journals Channel Estimation and Signal Detection in OFDM Systems using Deep Learning

2019 ◽  
Vol 8 (12S) ◽  
pp. 176-179
Keyword(s):  
Deep Learning ◽  
Channel Estimation ◽  
Signal Detection ◽  
Orthogonal Frequency Division Multiplexing ◽  
Minimum Mean Square Error ◽  
Ofdm Systems ◽  
Simulation Based ◽  
Channel Statistics ◽  
Channel Distortion ◽  
Deep Learning Model

this article presents “channel estimation and signal detection in OFDM systems by using deep learning”. OFDM stands for “Orthogonal Frequency Division Multiplexing”. This paper exploits end to end handling of wireless OFDM channels by deep learning. It is different from the existing OFDM receivers as it estimates the channel state information (CSI) explicitly and then estimated CSI is used to recover the transmitted symbols, thee proposed approach of deep learning implicitly estimates CSI and the transmitted symbols are recovered directly. The online transmitted data is directly recovered by the offline training a deep learning model using simulation based channel statistics generated data for addressing channel distortion. The performance comparable to “minimum mean square error” (MSME) estimator with transmitted symbols is detected by using deep learning based channel distortion. Using fewer number of pilots, omitting cyclic prefix and in the existence of nonlinear clipping noise, the approach of deep learning is more robust as compared to traditional methods.

Efficient Two-Stage Discrete Bit-Loading Algorithms for OFDM Systems

2010 ◽  
Vol 59 (7) ◽  
pp. 3407-3416 ◽  
Author(s):  
Deqiang Wang ◽  
Yewen Cao ◽  
Laibo Zheng
Keyword(s):  
Ofdm Systems ◽  
Two Stage ◽  
Bit Loading ◽  
Discrete Bit Loading
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