OFDM-IDMA Sistemi İçin Genetik Algoritmaya Dayalı Biyo-İlhamlı Pilot Dizayn Yaklaşımı

Öz

Tarak-tipi pilot yerleştirme stratejisi kullanan bir kanal kestiricisinin veriminin, pilot tonların pozisyonlarının ayarlanarak kontrol edilebileceği iyi bilinmektedir. Bu makalede, bu durum dikkate alınarak, dikgen frekans bölmeli çoğullama-serpiştirme bölmeli çoklu erişim (OFDM-IDMA) sisteminde kanal kestiricisi olarak kullanılan en küçük kareler (LS) algoritmasının kestirim hassasiyetini maksimuma çıkarmak amacıyla, güçlü problem çözme yeteneğinden dolayı geniş bir kullanım yelpazesine sahip olan genetik algoritma (GA), pilot tonların optimizasyonunda kullanılmıştır. Bunun yanı sıra, GA’nın amaç fonksiyonu olarak kullanılan ortalama karesel hatanın (MSE) hesaplama yükünden, optimizasyon işlemi boyunca ilgili fonksiyonun üst sınırı kullanılarak kaçınılmıştır. MSE’nin üst sınırı, Gershgorin disk teoreminden faydalanılarak elde edilmiştir. Simülasyonlarda, önerilen GA’ya dayalı pilot yerleştirme stratejisi, eşit aralıklı ve rastgele pilot yerleştirme gibi geleneksel yöntemler ile, bit hata oranı (BER) ve MSE olarak bilinen iki adet kriter bakımından karşılaştırılmıştır. Simülasyon sonuçları, GA tabanlı pilot dizayn stratejisinin, kayda değer bir MSE ve BER performansı sağlayarak, dikkate alınan diğer yöntemler üzerinde çok açık bir üstünlük kurduğunu ortaya koymuştur.

Anahtar Kelimeler

• Kanal Kestirimi,Genetik Algoritma,OFDM-IDMA,Pilot Ton Dizaynı

Bio-Inspired Pilot Design Approach based on Genetic Algorithm for OFDM-IDMA Scheme

Öz

It is well known that the efficiency of a channel estimator employing the strategy of comb-type pilot placement can be controlled by adjusting the positions of pilot tones. In this paper, by considering this situation, in order to maximize the estimation precision of the least squares (LS) algorithm utilized as a channel estimator in orthogonal frequency division multiplexing – interleave division multiple access (OFDM-IDMA) scheme, the genetic algorithm (GA) possessing a wide range of uses due to its powerful problem solving capability was utilized in the optimization of pilot positions. Besides, the computational load of mean square error (MSE) which is used as the objective function of GA was avoided by employing its upper bound during the optimization process. The upper bound of MSE was achieved by utilizing the Gershgorin disc theorem. In the simulations, the suggested pilot arrangement strategy based on the GA was compared to the conventional techniques like equispaced and random pilot placements in point of two criteria known as bit error rate (BER) and MSE. Simulation results put forth that GA-based pilot design strategy establishes a very clear superiority over the other considered methods by providing significant MSE and BER performances.

Anahtar Kelimeler

• Channel Estimation,Genetic Algorithm,OFDM-IDMA,Pilot Tones Design

Kaynakça

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