CP‐Based SBHT‐RLS Algorithms for Tracking Channel Estimates in Multicarrier Modulation Systems

H Ali

doi:10.1155/2012/452806

Abstract

Cyclic prefix (CP) in multicarrier modulation systems has been considered as an alternative to the training sequences to track channel estimates. In this paper, two new algorithms are developed that exploit CP from their data detection part and employ systolic block Householder transformation recursive least squares (SBHT‐RLS) algorithms for channel tracking in multicarrier systems. The new methods are compared with the existing CP exploiting correlation matrix based block RLS (CMB‐RLS) channel tracking approach to outline their relative advantages. Aspects of computational complexity and parallel implementation are addressed, and the algorithms are tested in terms of their channel estimation and tracking capabilities. Performance of the algorithms is also evaluated for varying forgetting factor parameter values, constellation size, and word lengths. Floating‐point and fixed‐point simulations are tailored to illustrate pertinent tradeoffs.

Highlights

Over the last two decades, multicarrier modulation has received considerable interest for its use in wireless and wireline communication systems [1,2,3,4]. It has been adopted in many communication standards, including digital audio broadcasting (DAB) [5], digital video broadcasting (DVB) [6], high-speed modems over digital subscriber lines [4], and local area mobile wireless broadband [7]
Because Householder transformation (HT) generally outperforms Givens rotation (GR) and modified Gram-Schmidt (MGS) methods under finite precision computations, and in the context of our application the channel needs to be updated for each block input data matrix, we focus our attention to the QR decomposition (QRD)-RLS algorithm based on block HT
Only the first discrete multitone (DMT) symbol was sent as pure training sequence to identify the initial channel for fast convergence

Summary

Introduction

Over the last two decades, multicarrier modulation has received considerable interest for its use in wireless and wireline communication systems [1,2,3,4]. Because HT generally outperforms GR and MGS methods under finite precision computations (see the references in [16]), and in the context of our application the channel needs to be updated for each block input data matrix, we focus our attention to the QRD-RLS algorithm based on block HT. The derivation of the inverse factorization method in this paper is done by generalizing the Extended QRDRLS algorithm to block RLS case [28] For this reason, this method will be referred to as CP-based Extended SBHTRLS approach. We underscore here that this simple and straightforward derivation is different than the previous challenging work on block RLS using inverse factorizations in [29, 30] Computational complexity of this scheme is equivalent to the first proposed scheme, but unlike the first scheme it is fully amenable to VLSI implementation and results in improved steady-state performance. The meaning of other variables will be clear from the context

System Model

CP-Based SBHT-RLS Algorithms

Computational Complexity and Systolic Array Implementation

Simulation Results

Conclusion