The demand for high speed, reliable communication using available frequency spectrum results in a new technology called OFDM. Channel estimation has a vital role in finding the effect of the channel on OFDM signal. In this work, performance analysis and implementation of pilot aided channel estimation is investigated. Different channel estimation methods like Least Square, Minimum mean Square Error estimator, modified MMSE and LS methods are discussed in the proposed work. This paper concentrates on performance comparison of channel estimation in terms of Symbol error rate and Mean square error.

Analysis and implementation of channel estimation in OFDM system using pilot symbols

In this modern world, technology has improved a lot and wireless communications are much necessary. MIMO wireless technology is very much essential for providing increased connectivity and spectral efficiency combined with the reliability of advanced connectivity using what were previously considered as interference paths. The multiple access system is considered such that they provide the different methods in communication for multi-users. In this work, the iterative algorithm is used such that it helps in defining random array of signals and assigning the phase to the given measured amplitude. Different types of multiple access systems such as Non-Orthogonal multiple access (NOMA), Orthogonal multiple access (OMA) and Adaptive Orthogonal multiple access (AOMA)which are used to analyze transmission of multiple data stream over power domain in the presence of AWGN and Rayleigh channel. The data transmitted over the channel may vary due to some interference on its path. The signal strength is calculated in the receiver using the fading channel and the other noises that gets added in the channel. MATLAB software tool is used for simulation and the performance analysis in terms of average sum value i.e. the signal strength with respect to SNR for all the above mentioned multiple access techniques is compared. The simulation results clearly exhibits that NOMA outperforms the other two cases and is one of the promising technology for fifth generation wireless communications.

Implementation of MIMO OFDM NOMA System using Iterative Algorithm

This paper is focusing on the performance of the proposed exponentially weight recursive least square (EW-RLS) and normalized least mean square (NLMS) channel estimator using simulations, in the context of the communication system with MIMO antenna operating in outdoor environments. Different training rates and different Doppler frequencies are used to track time-variations of the channel. Three adaptive algorithms are considered; namely the least squares (LS), RLS algorithm and the least mean square (LMS) algorithm. In channel estimation, RLS is widely used especially for slow time-varying. Even though RLS is little bit complex compare to LMS, but it has faster convergence speed. The performance is evaluated in terms of the mean square error (MSE) of the channel estimate, and the system bit error rate (BER), for different Doppler frequencies (correspond to different mobility speeds). Simulation results have demonstrated that time-domain adaptive channel estimation and tracking in MIMO OFDM systems based on the decision directed (DD) EW-RLS and DD-NLMS is very effective in slowly to moderate time-varying fading channels. This paper provides analysis, evaluation and computer simulations in MATLAB.

Performance of channel estimation based on DD-EW RLS and NLMS for outdoor MIMO OFDM system

Multiple Input Multiple Output (MIMO) in combination with Orthogonal Frequency Division Multiplexing (OFDM) can provide spectrally efficient and ISI free communication. Channel estimation is of great importance in order to recover the signal at the receiver side. Therefore accurate channel state information is essential for proper detection and decoding in MIMO-OFDM wireless systems. To estimate channel state information various types of techniques are being deployed in these systems. Accuracy and precision of channel estimation depends on the techniques used for the purpose of estimating channel state information. The more the accuracy of the technique, more will be the accurate performance of the system. In this paper an enhanced adaptive channel estimation using RLMS technique has been purposed. It is the combination of LMS and RLS algorithm. This technique provides better performance which can be judged by the BER performance. Comparison of the technique is done with the simple LMS and LLMS which is the combination of two LMS algorithms. Simulation results show that the purposed algorithm outperforms the latter algorithms. BPSK and QPSK modulations are used for analysis purposes.

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Enhanced Adaptive Channel Estimation Technique for MIMO-OFDM Wireless Systems

MIMO-OFDM (multiple input multiple output-orthogonal frequency division multiplexing) is an excellent multiplexing technique with several advantages of very high data transmission rate and greater spectral efficiency. The conventional channel estimation algorithms such as Least Square (LS) & Minimum Mean Square Error (MMSE) estimation are utilized to retrieve the channel state information (CSI) from the receiver with certain limitations. The LS estimation is simple but Mean Square Error is higher than MMSE estimation. At the same time, MMSE estimation has lower MSE than LS estimation at low SNR values with high computation time. Both estimation techniques cannot reduce noise levels at the receiver. Efficient Genetic Algorithm (GA)-based optimized channel estimation is proposed in this paper to identify the best channel matrix from the existing LS and MMSE estimation algorithms and simulated using matlab. The result shows that GA-based estimation outperforms the LS and MMSE estimation in terms of less MSE.

/pdf/genetic-algorithm-based-optimized-channel-estimation-in-mimo-30mf5ma6a0.pdf

Genetic Algorithm-Based Optimized Channel Estimation in MIMO-OFDM System

In modern wireless communication systems, a combination of multiple-input multiple-output (MIMO) system with the orthogonal frequency division multiplexing (OFDM) technique can be used to achieve high data rate and &better spectral efficiency. A Channel estimation technique using pilot carriers for multiple input multiple output( MIMO) systems for a Rayleigh fading channel is proposed in this paper. The channel estimation is carried out with conventional Least Square (LS) and Minimum Mean Square (MMSE) estimation algorithms. The performance of MIMO-OFDM system is evaluated on the basis of Bit Error Rate (BER) and Mean Square Error (MSE) level.

I.P Akhila

Papers

Channel estimation analysis in MIMO-OFDM wireless systems