scholarly journals MBER Space Time Equalization assisted Multiuser Detection

2012 ◽  
pp. 47-50
Author(s):  
Yogeshwary B.H. ◽  
T.L. Purushottama ◽  
M Z Kurian
Keyword(s):  
Bit Error Rate ◽  
Error Rate ◽  
Minimum Mean Square Error ◽  
Space Time ◽  
Decision Feedback ◽  
Lms Algorithm ◽  
Mean Square ◽  
Least Mean Square ◽  
Estimation Errors ◽  
Time Equalization

A novel minimum bit-error rate (MBER) space–time-equalization (STE)-based multiuser detector (MUD) is proposed for multiple-receive-antenna-assisted space-division multiple-access systems. It is shown that the MBER-STE-aided MUD significantly outperforms the standard minimum mean-square error design in terms of the achievable bit-error rate (BER). Adaptive implementations of the MBER STE are considered, and both the block-databased and sample-by-sample adaptive MBER algorithms are proposed. The latter, referred to as the least BER (LBER) algorithm, is compared with the most popular adaptive algorithm, known as the least mean square (LMS) algorithm. It is shown that in case of binary phase-shift keying, the computational complexity of the LBER-STE is about half of that required by the classic LMS-STE. Our simulation results demonstrate that the MBER ST-DFE assisted MUD is more robust to channel estimation errors as well as to potential error propagation imposed by decision feedback errors, compared to the MMSE ST-DFE assisted MUD.

scholarly journals Performance Enhancement of Coherent Optical OFDM System Using LMS Algorithm

2020 ◽  
Vol 1 ◽  
pp. 1-5
Author(s):  
Manisha Bharti
Keyword(s):  
Phase Noise ◽  
Bit Error Rate ◽  
Error Rate ◽  
Orthogonal Frequency Division Multiplexing ◽  
Performance Enhancement ◽  
Lms Algorithm ◽  
Frame Structure ◽  
Least Mean Square ◽  
Ofdm Systems ◽  
Ofdm System

Instability of the local oscillator causes phase noise – a phenomenon that is a disadvantage and is considered to be a major obstacle in the functioning of coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. An attempt has been made in this paper to reduce the effects of common phase errors generated by phase noise. In this paper, a least mean square (LMS) based algorithm is proposed for estimation of phase noise. Using this proposed algorithm, the major problem of phase ambiguity caused by cycle slip is avoided and the bit error rate is greatly improved. Further, there is no requirement for modifying the frame structure of OFDM using this algorithm. A CO-OFDM system with the 8-PSK technique is used to implement the algorithm concerned. Furthermore, the algorithm, using the 8-PSK modulation technique, is analyzed and compared with the existing QPSK technique and with other algorithms. The investigations reveal that 8-PSK outperforms existing LMS algorithms using other techniques and significantly reduces the bit error rate.

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.

scholarly journals Estimation of FBMC/OQAM Fading Channels Using Dual Kalman Filters

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Mahmoud Aldababseh ◽  
Ali Jamoos
Keyword(s):  
Fading Channels ◽  
Kalman Filters ◽  
Fading Channel ◽  
Minimum Mean Square Error ◽  
Least Square ◽  
Lms Algorithm ◽  
Mean Square ◽  
Least Mean Square ◽  
Recursive Least Square ◽  
Channel Statistics

We address the problem of estimating time-varying fading channels in filter bank multicarrier (FBMC/OQAM) wireless systems based on pilot symbols. The standard solution to this problem is the least square (LS) estimator or the minimum mean square error (MMSE) estimator with possible adaptive implementation using recursive least square (RLS) algorithm or least mean square (LMS) algorithm. However, these adaptive filters cannot well-exploit fading channel statistics. To take advantage of fading channel statistics, the time evolution of the fading channel is modeled by an autoregressive process and tracked by Kalman filter. Nevertheless, this requires the autoregressive parameters which are usually unknown. Thus, we propose to jointly estimate the FBMC/OQAM fading channels and their autoregressive parameters based on dual optimal Kalman filters. Once the fading channel coefficients at pilot symbol positions are estimated by the proposed method, the fading channel coefficients at data symbol positions are then estimated by using some interpolation methods such as linear, spline, or low-pass interpolation. The comparative simulation study we carried out with existing techniques confirms the effectiveness of the proposed method.

scholarly journals Maximal Ratio Combining Using Channel Estimation in Chaos Based Pilot-Added DS-CDMA System with Antenna Diversity

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Meher Krishna Patel ◽  
Stevan M. Berber ◽  
Kevin W. Sowerby
Keyword(s):  
Channel Estimation ◽  
Bit Error Rate ◽  
Error Rate ◽  
Lms Algorithm ◽  
Maximal Ratio Combining ◽  
Cdma System ◽  
Decision Variable ◽  
Antenna Diversity ◽  
Least Mean Square ◽  
Channel Estimator

This paper presents an adaptive multiuser transceiver scheme for DS-CDMA systems in which pilot symbols are added to users’ data to estimate complex channel fading coefficients. The performance of receiver antenna diversity with maximal ratio combining (MRC) technique is analyzed for imperfect channel estimation in flat fading environments. The complex fading coefficients are estimated using least mean square (LMS) algorithm and these coefficients are utilized by the maximal ratio combiner for generating the decision variable. Probability of error in closed form is derived. Further, the effect of pilot signal power on bit error rate (BER) and BER performance of multiplexed pilot and data signal transmission scenario are investigated. We have compared the performance of added and multiplexed pilot-data systems and concluded the advantages of both systems. The proposed CDMA technique uses the chaotic sequence as spreading sequence. Assuming proper synchronization, the computer simulation results demonstrate the better bit error rate performance in the presence of channel estimator in the chaotic based CDMA system and the receiver antenna diversity technique further improves the performance of the proposed system. Also, no channel estimator is required if there is no phase distortion to the transmitted signal.

A LMS-Based Equalization Algorithm for 28Gbaud PM-MQAM Optical Coherent System

2013 ◽  
Vol 760-762 ◽  
pp. 268-272
Author(s):  
Dong Yan ◽  
Xian Zhou ◽  
Li Min Xia ◽  
Xiao Yun Wu ◽  
Na Na Zhang
Keyword(s):  
Steady State ◽  
Bit Error Rate ◽  
Error Rate ◽  
Coherent System ◽  
Mean Square ◽  
Least Mean Square ◽  
Equalization Algorithm ◽  
Polarization Multiplexing ◽  
Least Mean Square Algorithm

In this paper, we presented an improved equalization algorithm which use Least Mean Square algorithm (LMS) training-based as pre-convergence, after reaching the threshold, equalization switches to directed decision LMS to compensate a various of impairs and decrease bit error rate (BER) to achieve better performance in the steady-state, the experiment is based on a 28GbaudMQAM polarization multiplexing optical coherent system.

PSO- AND GA-BASED NARROWBAND JAMMER EXCISION IN CDMA

2010 ◽  
Vol 19 (01) ◽  
pp. 123-138 ◽  
Author(s):  
IMRAN ZAKA ◽  
HABIB UR REHMAN ◽  
SYED ISMAIL SHAH ◽  
JAMIL AHMAD
Keyword(s):  
Bit Error Rate ◽  
Error Rate ◽  
Computational Intelligence ◽  
Optimization Problem ◽  
Narrow Band ◽  
Mean Square ◽  
Least Mean Square ◽  
Rate Performance ◽  
Convergence Criteria ◽  
Swarm Optimization

Narrowband jammer excision is formulated as an optimization problem in this paper. Optimal filter weights are calculated/searched for by the computational intelligence techniques. We compare the error rate performance, complexity, and implementation issues of various computational intelligence techniques like Particle Swarm Optimization (PSO), Genetic Algorithm, and Least Mean Square (LMS). These techniques update the excision filter weights iteratively till the convergence criteria has been achieved. Bit Error Rate performance shows these techniques effectively suppress the Narrow Band Interference. It has been observed that PSO-based algorithm with tuned parameters outperforms other schemes of PSO and the other algorithms. It approaches the optimum performance in fewer iterations with ease in implementation.

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