A Novel Adaptive Pilot Placement Algorithm for Channel Estimation in OFDM Based Systems

Year 2021, Volume: 9 Issue: 4, 943 - 964, 04.12.2021

Fatih Ayvenli , Çetin Kurnaz

https://doi.org/10.36306/konjes.866310

Abstract

The orthogonal frequency division multiplexing (OFDM) system, which is one of the multi-carrier communication systems, has been widely used due to its ability to provide high-speed data communication using bandwidth effectively and its resistance to echo delays. In OFDM system, the disturbing effects of the wireless communication channel can be reduced by estimating the channel in the receiver. In this study, a novel channel estimation method with a pilot placement algorithm which can adaptively change according to the structure of the channel is proposed for the OFDM system. The proposed algorithm is based on placing the pilot signals more frequently in the regions with deep fading of the channel. From the simulation results, it is seen that the proposed adaptive channel estimation algorithm gives better results than the classical channel estimation algorithms, and provides an improvement of up to 11.6 dB in bit error rate (BHO) performance. In addition, unlike the studies in the literature, a new mathematical expression is proposed in the last part of the study to determine the threshold level of the regions where the pilot frequency will be increased in the frequency domain of channel.

Keywords

OFDM, Channel estimation, Irregular pilot placement, Mobile radio channel

OFDM SİSTEMLERİNDE KANAL KESTİRİMİ İÇİN YENİ BİR UYARLAMALI PİLOT YERLEŞİM ALGORİTMASI

Abstract

Çok taşıyıcılı haberleşme sistemlerinden biri olan dikgen frekans bölmeli çoğullama (orthogonal frequency division multiplexing, OFDM) sistemi, bant genişliğini etkin kullanarak yüksek hızlı veri haberleşmesine olanak sağlaması ve yankı gecikmelerine karşı dayanıklılığı nedeniyle günümüzde yaygın olarak kullanılmaktadır. OFDM sisteminde gezgin iletim kanalının bozucu etkileri alıcıda kanal kestirimi yapılarak azaltılabilir. Bu çalışmada OFDM sistemi için kanalın yapısına göre uyarlamalı olarak değişebilen yeni bir pilot yerleşimli kanal kestirim algoritması önerilmiştir. Önerilen algoritma kanalın derin sönümlenmelerinin olduğu bölgelere daha sık pilot yerleştirilmesi temeline dayanmaktadır. Benzetim sonuçlarından, önerilen uyarlamalı kanal kestirim algoritmasının klasik kanal kestirim algoritmalarına göre daha iyi sonuç verdiği ve bit hata oranı (BHO) başarımında 11.6 dB’e varan bir iyileşme sağladığı görülmüştür. Ayrıca literatürdeki çalışmalardan farklı olarak bu çalışmada frekans düzleminde pilot sıklığının artırılacağı bölgelerin eşik seviyesini belirlemek için yeni bir matematiksel ifade önerilmiştir.

Keywords

OFDM, Kanal kestirimi, Düzensiz pilot yerleşimi, Gezgin iletim kanalı

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