Joint modulation classification and antenna number detection for MIMO systems

Noncooperative classification of the modulation type of communication signals finds application in both civilian and military contexts. Existing modulation classification methods for multiple-input multiple-output (MIMO) communication systems commonly require a priori information on the number of transmit antennas employed by the multiantenna transmitter, which, in most of the noncooperative scenarios involving modulation classi- fication, is unknown and needs to be blindly extracted from the received signal. Since the problems of MIMO modulation classification and detection of the number of transmit antennas are highly coupled, we propose a decision theoretic approach for spatial multiplexing MIMO systems that considers these two tasks as a joint multiple hypothesis testing problem. The proposed method exhibits a high performance even in moderate to low SNR regimes while requiring no a priori knowledge of the channel state information and the noise variance

A low-complexity time-domain MMSE channel estimator for space-time/frequency block-coded OFDM systems

Focusing on transmit diversity orthogonal frequency-division multiplexing (OFDM) transmission through frequency-selective channels, this paper pursues a channel estimation approach in time domain for both space-frequency OFDM (SF-OFDM) and space-time OFDM(ST-OFDM) systems based on AR channel modelling. The paper proposes a computationally efficient, pilot-aided linear minimum mean-square-error (MMSE) time-domain channel estimation algorithm for OFDM systems with transmitter diversity in unknown wireless fading channels. The proposed approach employs a convenient representation of the channel impulse responses based on the Karhunen-Loeve (KL) orthogonal expansion and finds MMSE estimates of the uncorrelated KL series expansion coefficients. Based on such an expansion, no matrix inversion is required in the proposed MMSE estimator. Subsequently, optimal rank reduction is applied to obtain significant taps resulting in a smaller computational load on the proposed estimation algorithm. The performance of the proposed approach is studied through the analytical results and computer simulations. In order to explore the performance, the closed-form expression for the average symbol error rate (SER)probability is derived for the maximum ratio receive combiner(MRRC). We then consider the stochastic Cramer-Rao lower bound(CRLB) and derive the closed-form expression for the random KL coefficients, and consequently exploit the performance of the MMSE channel estimator based on the evaluation of minimum Bayesian MSE. We also analyze the effect of a modelling mismatch on the estimator performance. Simulation results confirm our theoretical analysis and illustrate that the proposed algorithms are capable of tracking fast fading and improving overall performance. Copyright © 2006 Hindawi Publishing Corporation. All rights reserved

Maximum likelihood approach for localization of sources in 3-D space

Bu çalışmanın amacı, anten dizilimi ile aynı düzlemde bulunmayan 3 boyutlu uzayda bulunan kaynakların konumlarının kestirimidir. Kaynak konumları, 2 boyutlu dikdörtgen anten diziliminde toplanan verileri kullanan en büyük olabilirlik kestirimcisi ile belirlenmiştir. En büyük olabilirlik kestirimcisi, diğer kestirim yöntemlerine göre bir çok avantaja sahip olmasına rağmen işlemsel yoğunluğu olan bir algoritmadır. Bu işlemsel yoğunluk, çok boyutlu arama probleminden kaynaklanmaktadır. Karşılaşılan işlemsel yoğunluk, özyinelemeli beklenti en büyükleme algoritmasının ilgilenilen probleme uyarlanmasıyla ortadan kaldırılmıştır. Ayrıca, geliştirilen kestirimcinin başarımının incelenebilmesi için yansız bir kestirimci için alt sınırı oluşturan Cramer-Rao Sınırları çıkarılmıştır. Benzetim örneklerinden kullanılan yöntemin özellikle yüksek sinyal gürültü oranlarında oldukça iyi sonuçlar verdiği gözlemlenmiştir.  Anahtar Kelimeler: Kaynak yerelleştirme, en büyük olabilirlik, beklenti en büyükleme, Cramer-Rao sınırları.Various estimation methods have been proposed for localization  of passive sources till now. Most of these studies assumed, sources were at the same plane with antenna array. This assumption may be inappropriate for some applications in real world. The goal of this study is to estimate unknown locations of sources that is not at same plane with antenna array but in 3-D space. Locations of the sources are determined by maximum likelihood estimator that uses data collected by a 2-D rectangular array. Maximum Likelihood Method is chosen as the estimator since it has better resolution performance than the conventional methods in the presence of less number and highly correlated source signal samples and low signal to noise ratio. Besides these superiorities, stability, asymptotic unbiasedness, asymptotic minimum variance properties and bringing no restrictions on the antenna array are the additional reasons for the decision of this method. Despite these advantages, Maximum Likelihood Estimator has computational complexity. This problem arises from multidimensional search problem. Computational complexity was overcome by adapting iterative Expectation Maximization algorithm to the problem at hand. Furthermore, Cramer-Rao bounds that is the lower bound of any unbiased estimator are derived for analyzing the accuracy performance of the proposed algorithm. It was observed that the proposed algorithm gave satisfactory results especially for high signal to noise ratios.Keywords: Source localization, maximum likelihood, expectation maximization, Cramer-Rao bounds

Blind phase noise estimation in OFDM systems by sequential Monte Carlo method

In this paper, based on a sequential Monte Carlo method, a computationally efficient algorithm is presented for estimating the residual phase noise, blindly, generated at the output the phase tracking loop employed in OFDM systems. The basic idea is to treat the transmitted symbols as "missing data" and draw samples sequentially of them based on the observed signal samples up to time t. This way, the Bayesian estimates of the phase noise is obtained through these samples, sequentially drawn, together with their importance weights. The proposed receiver structure is seen to be ideally suited for high-speed parallel implementation using VLSI technology. © 2006 Springer

Blind data detection in the presence of PLL phase noise by sequential Monte Carlo method

In this paper, based on a sequential Monte Carlo method, a computationally efficient algorithm is presented for blind data detection in the presence of residual phase noise generated at the output the phase tracking loop employed in a digital receiver. The basic idea is to treat the transmitted symbols as" missing data" and draw samples sequentially of them based on the observed signal samples up to time t. This way, the Bayesian estimates of the phase noise and the incoming data are obtained through these samples, sequentially drawn,together with their importance weights. The proposed receiver structure is seen to be ideally suited for high-speed parallel implementation using VLSI technology. © 2006 IEEE

The effect of coracoid process transfer on the surgical procedures of shoulder instability

Amaç: Rekürrent anterior dislokasyon görülen omuzlarda, cavitas glenoidalis'in antero-inferior kenarında kemik kaybı saptanmaktadır. Bu omuzlarda, defektin büyüklüğü, omuz instabilitesinin derecesini etkilemektedir. Bu nedenle, processus coracoideus transferindeki temel problem, kemik grefti ihtiyacının olup olmadığıdır ve bu da bir ölçüde cavitas glenoidalis'teki defektin büyüklüğü ile ilişkilidir. Processus coracoideus transferi sonrasında, bu yöntemin cavitas glenoidalis'in yüzey alanına olan etkisini kantitatif olarak belirlemek gerekir. Bundan dolayı, bu çalışmanın amacı, kadavra omuzlarında, omuz instabilitesinin cerrahi tedavi yöntemlerinden olan processus coracoideus transferinin, cavitas glenoidalis'in yüzey alanına olan etkisininin saptanmasıdır. Çalışma tasarımı: Kadavra, laboratuvar çalışması. Gereç ve yöntem: Omuz diseksiyonu yapılan otuz kadavra scapulasında, cavitas glenoidails'in antero-inferior kısmında %21'lik ve %34'lük kemik defekti oluşturuldu ve daha sonra Latarjet yöntemi uygulandı. Her bir cavitas glenoidalis'in, milimetrik ölçek kullanılarak, Canon 400B (55 mm objektif) fotoğraf makinası ile, defekt öncesi ve Latarjet yöntemi sonrası, yüzey alanlarının fotoğrafları çekildi. Bu fotoğraflar bilgisayara aktarıldı. UTHSCSA Image Tool 3.0 bilgisayar programı kullanılarak, cavitas glenoidalis'in yüzey alanları hesaplandı. Bulgular: Cavitas glenoidalis'in defekt öncesi alanı ortalama 969,98 + 129,95 mm2 idi. %21 ve % 34'lük defekt alanlarına uygulanan Latarjet yöntemi sonrası, cavitas glenoidalis'in alanı, sırasıyla, ortalama 1133,80 + 119,65 mm2 ve 1006,50 + 110,69 mm2 olarak ölçüldü. %21 ve % 34'lük defekt oluşturulan vakalarda, defekt öncesi ve Latarjet yöntemi sonrası, cavitas glenoidalis'in yüzey alanları arasında istatistiksel olarak anlamlı bir fark saptandı (sırasıyla, p=0.000 ve p=0.025). Sonuç: Processus coracoideus transferi (Latarjet yöntemi), cavitas glenoidalis'in yüzey alanını anlamlı olarak arttırmaktadır. Background: Bone loss of the anteroinferior rim of the glenoid is observed in shoulders with recurrent anterior dislocation. In such shoulders, the size of the defect affects the degree of shoulder instability. Thus, before coracoid process transfer procedures are attempted, the need for bone grafting is a major clinical concern and depends at least partly on the size of the glenoid defect. After the coracoid process transfer is performed, the effect of this procedure on surface area of the glenoid cavity is need to be quantified. The purpose of this study, therefore, was to determine the effect of coracoid process transfer on surface area of the glenoid cavity of cadaveric shoulders in the surgical procedures of shoulder instability. Study Design: A cadaveric laboratory study. Methods: After the shoulder dissection, osseous defects of 21% and 34% of anteroinferior part of the glenoid surface area were created stepwise in 30 cadaveric scapulae, and Latarjet procedure was performed, respectively. Intact and postoperative surface area of the glenoid cavities were photographed, with Canon 400B (55 mm objective) and with a scale placed next to each specimen to indicate its relative size on the photographs. The images were loaded on a computer. The surface area of the photoghraphed glenoid cavities were calculated with use of UTHSCSA Image Tool 3.0 software. Results: The mean surface area of intact glenoid cavity was 969,98 + 129,95 mm2. The postoperative mean surface area of 21% and %34 defective glenoid cavity were 1133,80 + 119,65 mm2 and 1006,50 + 110,69 mm2, respectively. There was a statistically significant difference between the means of surface area of intact glenoid cavity and postoperative surface area of 21% and %34 defective glenoid cavity, (p=0.000, p=0.025; respectively). Conclusion: Coracoid process transfer (Latarjet procedure) significantly increases surface area of glenoid cavity

The effect of coracoid process transfer on the surgical procedures of shoulder instability

Amaç: Rekürrent anterior dislokasyon görülen omuzlarda, cavitas glenoidalis'in antero-inferior kenarında kemik kaybı saptanmaktadır. Bu omuzlarda, defektin büyüklüğü, omuz instabilitesinin derecesini etkilemektedir. Bu nedenle, processus coracoideus transferindeki temel problem, kemik grefti ihtiyacının olup olmadığıdır ve bu da bir ölçüde cavitas glenoidalis'teki defektin büyüklüğü ile ilişkilidir. Processus coracoideus transferi sonrasında, bu yöntemin cavitas glenoidalis'in yüzey alanına olan etkisini kantitatif olarak belirlemek gerekir. Bundan dolayı, bu çalışmanın amacı, kadavra omuzlarında, omuz instabilitesinin cerrahi tedavi yöntemlerinden olan processus coracoideus transferinin, cavitas glenoidalis'in yüzey alanına olan etkisininin saptanmasıdır. Çalışma tasarımı: Kadavra, laboratuvar çalışması. Gereç ve yöntem: Omuz diseksiyonu yapılan otuz kadavra scapulasında, cavitas glenoidails'in antero-inferior kısmında %21'lik ve %34'lük kemik defekti oluşturuldu ve daha sonra Latarjet yöntemi uygulandı. Her bir cavitas glenoidalis'in, milimetrik ölçek kullanılarak, Canon 400B (55 mm objektif) fotoğraf makinası ile, defekt öncesi ve Latarjet yöntemi sonrası, yüzey alanlarının fotoğrafları çekildi. Bu fotoğraflar bilgisayara aktarıldı. UTHSCSA Image Tool 3.0 bilgisayar programı kullanılarak, cavitas glenoidalis'in yüzey alanları hesaplandı. Bulgular: Cavitas glenoidalis'in defekt öncesi alanı ortalama 969,98 + 129,95 mm2 idi. %21 ve % 34'lük defekt alanlarına uygulanan Latarjet yöntemi sonrası, cavitas glenoidalis'in alanı, sırasıyla, ortalama 1133,80 + 119,65 mm2 ve 1006,50 + 110,69 mm2 olarak ölçüldü. %21 ve % 34'lük defekt oluşturulan vakalarda, defekt öncesi ve Latarjet yöntemi sonrası, cavitas glenoidalis'in yüzey alanları arasında istatistiksel olarak anlamlı bir fark saptandı (sırasıyla, p=0.000 ve p=0.025). Sonuç: Processus coracoideus transferi (Latarjet yöntemi), cavitas glenoidalis'in yüzey alanını anlamlı olarak arttırmaktadır. Background: Bone loss of the anteroinferior rim of the glenoid is observed in shoulders with recurrent anterior dislocation. In such shoulders, the size of the defect affects the degree of shoulder instability. Thus, before coracoid process transfer procedures are attempted, the need for bone grafting is a major clinical concern and depends at least partly on the size of the glenoid defect. After the coracoid process transfer is performed, the effect of this procedure on surface area of the glenoid cavity is need to be quantified. The purpose of this study, therefore, was to determine the effect of coracoid process transfer on surface area of the glenoid cavity of cadaveric shoulders in the surgical procedures of shoulder instability. Study Design: A cadaveric laboratory study. Methods: After the shoulder dissection, osseous defects of 21% and 34% of anteroinferior part of the glenoid surface area were created stepwise in 30 cadaveric scapulae, and Latarjet procedure was performed, respectively. Intact and postoperative surface area of the glenoid cavities were photographed, with Canon 400B (55 mm objective) and with a scale placed next to each specimen to indicate its relative size on the photographs. The images were loaded on a computer. The surface area of the photoghraphed glenoid cavities were calculated with use of UTHSCSA Image Tool 3.0 software. Results: The mean surface area of intact glenoid cavity was 969,98 + 129,95 mm2. The postoperative mean surface area of 21% and %34 defective glenoid cavity were 1133,80 + 119,65 mm2 and 1006,50 + 110,69 mm2, respectively. There was a statistically significant difference between the means of surface area of intact glenoid cavity and postoperative surface area of 21% and %34 defective glenoid cavity, (p=0.000, p=0.025; respectively). Conclusion: Coracoid process transfer (Latarjet procedure) significantly increases surface area of glenoid cavity

Immunohistochemical evaluation of VEGF, EGF-r and TGF-α in placental bed of preeclamptic pregnancies

AMAÇ: Preeklamptik hastaların plasental yataklarında, immünohistokimyasal boyama yöntemi ile, vasküler endotelial büyüme faktörü (VEGF), epidermal büyüme faktörü receptörü (EGF-r) ve transforming büyüme faktörü alfa’nın (TGF-α) araştırılması. Planlama: Prospektif kohort çalışma. METOD: Çalışma grubunda preeklamptik 12 vaka ve kontrol grubundaki 10 normal gebelik vakasından sezaryen doğum esnasında plasental yatak biyopsileri alındı. Biyopsi örnekleri, anti-VEGF, anti-EGF-r ve anti-TGF-α antikorları ile yapılan immünohistokimyasal boyama sonrası, ışık mikroskopu ile incelendi. Boyanma yoğunluğu semikantitatif olarak derecelendirildi ve grupları bilmeyen 2 histopatolog tarafından H-skorları hesaplandı. SONUÇLAR: Çalışma grubunda myometrium ve desiduadaki VEGF ekspresyonu anlamlı olarak düşük bulundu (sırasıyla 77.2±25.4/134±44.3, p=0.007; 170.2±17/194.1±20.7, p=0.017); EGF-r ekspresyonu da çalışma grubunda myometrium ve desiduada anlamlı olarak düşük idi (p0.05). YORUM: Preeklamptik hastaların plasental yataklarında, anjiogenezisde önemli rol oynayan, VEGF ve EGF-r’ün ekspresyonu anlamlı olarak düşükdür.OBJECTIVE: The aim of the study is to determine vascular endothelial growth factor (VEGF), epidermal growth factor receptor (EGF-r) and transforming growth factor alpha (TGF-α) with the immunohistochemical staining at the placental bed biopsies of patients with preeclampsia. Design: Prospective cohort study. METHODS: Biopsies from the placental bed were obtained from twelve patients with preeclapmsia and ten patients of control group during the cesarean section. The sections from the biopsies were subjected to immunohistochemical staining by using anti-VEGF, anti-EGF-r and anti-TGF-α antibodies and were examined by light microscopy. The staining intensities were graded semi-quantitatively and the H-scores were calculated by two histopatologist who were blinded to the groups. RESULTS: The VEGF expression was significantly lower in both myometrium and decidua of preeclamptic women compared to controls (77.2±25.4 versus 134±44.3, p=0.007; 170.2±17 versus 194.1±20.7, p=0.017, respectively).EGF-r expression also was significantly lower at both decidua and myometrium in the preeclamptic group (p<0.05). TGF-α expression of myometrium and decidua was not significantly different between two groups (p>0.05). CONCLUSION: VEGF and EGF-r expression is significantly lower at the placental bed in patients with preeclampsia