Energy Efficient Doppler Assisted Channel Estimation for Highly Mobile OFDM Systems

Mateen Ashraf,Kyung-Geun Lee,Adnan Shahid,Woon-Young Yeo

doi:10.1155/2015/892151

Abstract

The complexity of channel estimation algorithms is of critical importance in high mobility orthogonal frequency division multiplexing (OFDM) systems. To reduce the complexity of the algorithm, the existing channel estimation algorithms take advantage of the correlations between the channel coefficients. However, they do not take into account the variations of the correlations with the delay tap. In this paper, we consider the change in correlation between channel coefficients for different delay taps. By considering these variations, the number of computations needed for channel estimation can be decreased. This results in a reduction in the circuit energy. The simulation results show that the proposed scheme consumes less total energy per bit for transmission distances less than about 170 m when the mobile speed is 324 Kmph.

Highlights

orthogonal frequency division multiplexing (OFDM) has been adopted in many standards due to its improved performance in the presence of frequency selective channels
The number of reference channel coefficients used for the existing scheme in [2] is 48, while the number of reference channel coefficients for the proposed scheme is different for different speeds
We can optimize the selection of reference channel coefficients this will increase the complexity of the receiver because the optimal reference coefficients will vary for every block of channel realization

Summary

Introduction

OFDM has been adopted in many standards due to its improved performance in the presence of frequency selective channels. We show that by utilizing the variations of correlation coefficients for different delay taps it is possible to reduce the complexity and subsequently the circuit energy consumption of the channel estimation algorithm. In this paper we design a new scheme that exploits the fact that correlation among channel coefficients for the same time differences of smaller delay taps is higher than their larger counterparts [4]. This helps in reducing the reference channel coefficients for smaller delay taps. (ii) The variation in the correlation coefficient for different delay taps is exploited to decrease the number of time domain markers in the estimation process. In the following we will use bold face capital letters to represent matrices and bold face small letters to represent vectors, (⋅)T represents the transpose operation, (⋅)∗ represents the conjugation operation, (⋅)H represents the Hermitian transpose, xrepresents the approximation of x, xrepresents the Fourier representation of x, and E[⋅] represents the statistical expectation

System Model

Proposed Scheme

Simulation Results

Conclusions