1529 words - 7 pages

Adaptive Filter is a the part of Digital signal system which is widely used in the modern communication system. The basic application of the adaptive filter such as adaptive noise cancellation, channel equalization, system identification and adaptive beam forming. So its implementation is a great deal and that much important field in the digital system world. As we know intersymbol interference (ISI) caused by the multipath in band limit frequency selective time dispersion channel distort the transmitted signal. In this paper, we are concentrated on modifying the algorithm for the adaptive filter and proposed Modified Variable Step Size Leaky LMS (MVSS-LLMS) which improves the channel ...view middle of the document...

MIMO is a technology which improves the performance of the wireless system. MIMO is referred as Multiple Input and Multiple Output i.e a radio links with multiple transmitter antennas and multiple receiver antennas. While transmission of the radio signal from the transmitter antenna through space might be possibilities of signal path effected by reflection, diffraction which result in multipath signal at the receiver antenna which causes interferences and signal fading. MIMO technology multiplexing those multipath signals with advance DSP algorithm in order to improve the bandwidth efficiency and range [2].

MIMO and OFDM techniques are combined in an attractive method for wireless system, which is refer as MIMO-OFDM [16]. The generalized block diagram of MIMO-OFDM system is shown in figure 1. Least mean square (LMS), Kalman filter, Normalized Least mean square (NLMS) and variable step size LMS (VSSLMS) are some of the numerical computational techniques that have been applied for Noise Cancellation in wireless communication. Along with it, soft computing technique, for example, fuzzy logic, neural networks, simulated annealing are also some of new the techniques used for frequency estimation [1]. In this paper, we are given more concentration on the approach based on LMS algorithm. LMS algorithm is mostly used conventional algorithm for the designing of adaptive filter. Due to its computational simplicity, ease of implementation and unbiased convergence [10].

The main goal of this paper is to modified this algorithm and proposed a new algorithm Modified Variable Step Size Leaky LMS (MVSS-LLMS) that should be very easy to control in this real world application.

In the remaining portion of this paper describes the overview of the Adaptive Channel Estimator is explain in Section II. Section III describes the MSE (Mean Square Error) analysis of LMS, RLS, VLLMS and proposed MVSS-LLMS algorithm. Section IV explains about the architecture of the LMS and proposed algorithm. The performance analysis is describe in section V. Finally its simulation results are represented in section VI and in section VII gives the conclusion that we derived from the results.

II. ADAPTIVE CHANNEL ESTIMATION TECHNIQUE

Channel Estimation is the key factor in the communication system especially in OFDM [7]. Now a day the 3G wireless system is widely used, therefore channel estimation problem is more important as many signal processing technique requires the knowledge of channel information in order to meet the challenges of throughput and performance. Estimation of channel becomes more difficult because both the multipath effect and fading effect have been considered in 3G system [8].

We have considered the channel is rapidly time-varying in adaptive channel estimation. An adaptive algorithm is a process that changes its parameters with changing environment [4],[5]. The channel estimation methods like Least square estimation which uses adaptive...

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