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Rice, Michael, Md Shah Afran, and Mohammad Saquib. "MMSE Equalization for Aeronautical Telemetry Channels." International Foundation for Telemetering, 2014. http://hdl.handle.net/10150/577447.
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ITC/USA 2014 Conference Proceedings / The Fiftieth Annual International Telemetering Conference and Technical Exhibition / October 20-23, 2014 / Town and Country Resort & Convention Center, San Diego, CAThis paper presents performance analysis of the minimum mean squared error (MMSE) equalizers applied to aeronautical telemetry channels. The challenge for equalizing received samples of the modulated signal lies in the fact that the underlying continuous-time SOQPSK-TG waveform is not wide-sense stationary. However it is assumed so in order to meet real-time implementation requirements. Two approximations of the autocorrelation function of the SOQPSK-TG waveform are used for designing MMSE equalizers. Their performance are investigated against the zero forcing equalizer for measured aeronautical telemetry channels.
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Garcia-Alis, Daniel. "On adaptive MMSE receiver strategies for TD-CDMA." Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366896.
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Yildirim, Recep Ali. "Mmse Based Iterative Turbo Equalization For Antenna Switching Systems." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612480/index.pdf.
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In this thesis, we study the performance of an antenna switching (AS) system in comparison to an Alamouti coded system. We analyze the outage probabilities and propose minimum mean-squared error based iterative equalizers for both systems. We see from the outage probability analysis of both systems that the AS system may achieve the same diversity order of the Alamouti coded scheme contingent on the transmission rate and constellation size. In the proposed receiver, MMSE equalization and channel decoding are jointly carried out in an iterative fashion. We use both hard and soft decision channel decoders in our simulations. It is observed that the Alamouti based scheme performs better when the channel state information is perfect. The Alamouti scheme also performs better than the AS scheme when the channel state information is imperfect in hard decision channel decoder case and a random interleaver is used. On the other hand, if a random interleaver is not used, AS scheme performs remarkably better than the Alamouti scheme in hard decision channel decoder case. In a soft decision channel decoder case, when the channel state information is imperfect, the AS scheme performs approximately a 2 dB better than the Alamouti scheme. Moreover, there is approximately a 3 dB performance gain if a soft decision channel decoder is used instead of hard decision.
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Afran, Md Shah, Mohammad Saquib, and Michael Rice. "SPARSE MMSE EQUALIZER FOR GTR-STBC IN AERONAUTICAL TELEMETRY." International Foundation for Telemetering, 2017. http://hdl.handle.net/10150/626962.
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This paper investigates the performance of sparse minimum mean squared error (MMSE) equalizer for generalized time-reversed space-time block codes (GTR-STBC) in aeronautical telemetry. GTR-STBC equipped with MMSE equalizer performs the best trade-off between the signal-tonoise ratio and inter-symbol interference by allocating unequal power over aeronautical telemetry channels. However, aeronautical telemetry channels are in general consists of larger delay spreads which make the MMSE equalization of aeronautical channels with GTR-STBC computationally complex. Interestingly enough, in spite of larger delays aeronautical channels are made of few sparsely distributed multipaths and therefore their MMSE equalizers are highly compressible. In this paper, compressed sensing based greedy algorithm is used for the design of sparse MMSE equalizer and a convex curve-fitting algorithm is used to find the sub-optimum power allocation parameter at the same sparsity level for GTR-STBC. Our simulation results show that 75-90% of the non-zero equalizer taps can be reduced with a slight relaxation of the mean-squared error (or equivalentlyslight degradationof bit-errorrate performance). It isalso observedthat the optimum transmitter power profile for the sparse MMSE equalizer is different than that of the non-sparse equalizer.
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Pozo, Patricio Hector Aurelio Espinosa Del. "Funções cognitivas e memória em adultos com mais de 65 anos em Cumbayá, Quito DM, Equador." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/17/17138/tde-25042018-144433/.
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Introdução O envelhecimento populacional é uma realidade no Equador e este fato resulta em maior prevalência dos problemas mais frequentes em idosos, dentre eles, a deterioração das funções cognitivas. Objetivo Avaliar a função cognitiva, prevalência e fatores de risco associados ao declínio cognitivo e demência em pessoas com mais de 65 anos em Cumbayá-Quito, Equador. Métodos Este é um estudo de observação transversal que foi realizado em adultos com mais de 65 anos de idade. O Mini Exame do Estado Mental (MMSE), o Dementia Screening Interview (AD8) e a Mini Avaliação Nutricional (MNA) foram utilizados para avaliar o estado cognitivo e os hábitos nutricionais dessa população. Resultados Um total de 144 pacientes (idade média 75,3; 77,1% mulheres) fizeram parte deste estudo; 40% dos pacientes apresentaram testes positivos (AD8 e MMSE) consistentes com comprometimento cognitivo, possível demência. A idade (p<0,01), a escolaridade inferior (p <0,01), acidente vascular cerebral (p <0,01), hemorragia intracerebral (p<0,01), diabetes mellitus (p<0,01) e desnutrição (p<0,01) foram riscos significativos para o comprometimento cognitivo. O exercício (p <0,03) e o consumo de álcool (p=0,02) foram fatores de risco protetores para o declínio cognitivo nessa população. Gênero, etnia, localização, traumatismo craniano, doença de Parkinson, colesterol alto, diabetes, infarto do miocárdio, doença da tireóide, depressão, ansiedade, história familiar de demência não foram associados ao declínio cognitivo nessa população. Conclusões A prevalência de comprometimento cognitivo e possível demência aos 65 anos é de 18-21% e aos 85 anos é de 54-60% em Cumbayá, Quito, Equador. Os principais fatores de risco para deficiência cognitiva nesta população são idade, educação, desnutrição, acidente vascular cerebral e diabetes mellitus. Os fatores protetores para o declínio cognitivo foram o exercício e possivelmente o consumo moderado de álcool.Introduction Population aging is a reality in Ecuador and this fact results in a higher prevalence of the most frequent problems in the elderly, among them, the deterioration of cognitive functions. Objective To assess the cognitive function, prevalence, and risk factors associated with cognitive decline and dementia in people over 65 years of age in Cumbayá-Quito, Ecuador. Methods This is a cross-sectional observational study that was carried out in adults over 65 years of age. The Mini Mental Scale Examination (MMSE), Dementia Screening Interview (AD8) and Mini Nutritional Assessment (MNA) were used to assess the cognition status and nutritional habits of this population. Results A total 144 patients (mean age 75.3; 77.1% females) were part of this study; 40% of patients had positive tests (AD8 & MMSE) consistent with cognitive impairment, possible dementia. The age (p<0.01), lower school education (p<0.01), stroke (p<0.01), intracerebral hemorrhage (p<0.01), diabetes (p<0.01) and malnutrition (p<0.01), were significant risk factors for cognitive impairment. Exercise (p<0.03) and consumption of alcohol were a protective risk factor for cognitive decline in this population. Gender, ethnicity, location, head trauma, Parkinson disease, high cholesterol, diabetes, myocardial infarction, thyroid disease, depression, anxiety, family history of dementia were not associated with cognitive decline in this population. Conclusions The prevalence of cognitive impairment and possible dementia at the age of 65 years is 18-21% and at age 85 years is 54-60% in Cumbayá, Quito, Ecuador. The main risk factors for cognitive impairment in this population were age, education, malnutrition, stroke, and diabetes. Protective factors for cognitive decline were exercise and possibly modest consumption of alcohol.
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Kansanen, K. (Kimmo). "Wireless broadband single-carrier systems with MMSE turbo equalization receivers." Doctoral thesis, University of Oulu, 2005. http://urn.fi/urn:isbn:9514279336.
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Abstract
Broadband single-carrier modulated signals experience severe multipath distortion when propagating through the physical medium. Correcting the distortion with channel equalization is the foremost task of the detector. Prior information about the transmitted signals in the form of channel decoder feedback can significantly enhance equalization accuracy. An algorithm that iteratively performs channel decoding and equalization with prior information is generally denoted a turbo equalizer. This thesis focuses on turbo equalization with prior information using the principle of interference cancellation followed by minimum mean squared error (MMSE) filtering. Receiver algorithms, receiver convergence, and coding and modulation in the context of MMSE turbo equalization are studied.
Computationally efficient versions of the receiver algorithm through approximate time-average filtering, matched filtering, square-root time-variant filtering and frequency-domain filtering are studied. The frequency-domain turbo equalizer (FDTE) is found to exhibit both superior convergence and low computational complexity among the compared equalizer algorithms.
Multi-dimensional extrinsic information transfer (EXIT) charts are introduced for the purpose of tracking the convergence of the turbo equalization of layered MIMO transmissions. Generic properties of the equalizer EXIT functions defining the equalizer convergence are analyzed. The principles for detector ordering, maximum sum-rate code design and maximum rate symmetric design are derived from the properties of the multidimensional EXIT functions.
Semi-analytical EXIT charts are developed for the convergence analysis of the FDTE. The effects of channel parameters and the channel code are analyzed with semi-analytical methods. A new approach for the design of irregular low-density parity-check (LDPC) codes using a convergence outage principle is proposed. A performance gain is demonstrated in a single-input multiple output (SIMO) channel over non-optimized regular LDPC codes and irregular LDPC codes optimized for the AWGN channel. The outage convergence based design, which takes advantage of the semi-analytical convergence analysis method, is also extended to layered MIMO transmissions.
Quadrature amplitude modulation using multilevel bit-interleaved coded modulation (MLBICM) is studied as an alternative to regular bit-interleaved coded modulation (BICM) for highly bandwidth-efficient transmission in MMSE turbo equalized systems. A linear bit-to-symbol mapping is introduced that enables the use of a computationally efficient MMSE turbo equalizer at the receiver. The proposed coded modulation is compared with BICM in channel measurement data based simulations and found to exhibit superior robustness against changes in spatial channel parameters. An automatic repeat request (ARQ) configuration using one ARQ controller for each equally performing group of code levels is proposed. The configuration takes advantage of the unequal error protection (UEP) property of the coded modulation. The semi-analytical convergence analysis is extended to the multilevel modulated case and applied in a channel measurement based convergence evaluation. The construction of the MLBICM is found to have an inherently better convergence behavior than BICM. Finally, the outage convergence based channel code design is extended to the layered MIMO multilevel signalling case.
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Eneh, Titus Ikechukwu. "Adaptive MMSE multiuser receivers in MIMO OFDM wireless communication systems." Thesis, University of Greenwich, 2011. http://gala.gre.ac.uk/8041/.
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In a bid to cope with challenges of increasing demand for higher data rate, better quality of service, and higher network capacity, there is a migration from Single Input Single Output (SISO) antenna technology to a more promising Multiple Input Multiple Output (MIMO) antenna technology. On the other hand, Orthogonal Frequency Division Multiplexing (OFDM) technique has emerged as a very popular multi-carrier modulation technique, thus it is considered as a promising solution to enhance the data rate of future broadband wireless communication systems. The first contribution of this thesis is the development of a low complexity adaptive algorithm that is robust against slow and fast fading channel scenarios, in comparison to the conventional individual parameter estimation by E. Teletar in his famous paper of 1999. Implementing the Adaptive MMSE Receivers in MIMO OFDM systems which I refer to (AMUD MIMO OFDM), combines the adaptive minimum mean square error multiuser receiver's scheme with prior information of the channel and interference cancelation in the spatial domain, achieves enhanced joint channel estimation and signal detection which makes the new technique effectively mobile. A mathematical analysis and simulation results to estimate the Information Capacity of Mobile Communication system with MMSE DFE and OFDM receivers were investigated. The capacity of a stationary channel with ISI is achievable by both the single carrier MMSE DFE and multicarrier modulation over narrow sub channels with OFDM receivers. The achieved capacity result shows that in both techniques single carrier and multicarrier, apart from different implementations are essentially identical when it comes to achievable criteria for information channel capacity. Lastly, AMUD MIMO OFDM were compared with both adaptive vector pre-coding and iterative system and their performance were fantastic, results shows that it will assure transmission over a high channel capacity.
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Okada, Hiraku, Peter M. Grant, Ian W. Band, and Akira Ogawa. "Application of MMSE Multi-user Detection to CDMA Unslotted ALOHA System." IEEE, 2000. http://hdl.handle.net/2237/7806.
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Prendergast, Ryan Strong. "Modelling and MMSE reconstruction solutions for image and video super-resolution." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3307355.
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Thesis (Ph. D.)--University of California, San Diego, 2008.Title from first page of PDF file (viewed July 14, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 167-175).
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Qader, Sangar Nasruldeen. "Optimization of multidimensional equalizers based on MMSE criteria for multiuser detection." Thesis, University of Newcastle upon Tyne, 2016. http://hdl.handle.net/10443/3394.
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This thesis is about designing a multidimensional equalizer for uplink interleaved division multiple access (IDMA) transmission. Multidimensional equalizer can be classified into centralized and decentralized multidimensional equalizer. Centralized multidimensional equalizer (MDE) have been used to remove both inter-symbol interference (ISI) and multiaccess interference (MAI) effects from the received signal. In order to suppress MAI effects, code division multiple access (CDMA) has been used with MDE to minimize the correlation between users' signals. The MDE structure can be designed using linear equalizer (MLE) or decision feedback equalizer (MDFE). Previous studies on MDE employed adaptive algorithms to estimate filter co-effi cients during the training mode, i.e. the symbol equalization was not optimal, for two users. In our work, we applied MDE on IDMA receiver for multipath selective fading channels and also derived new equations to obtain the optimal filter taps for both types of MDE equalizers, i.e. MDFE and MLE, based on the minimum mean square error (MMSE) criterion. The optimal filter taps are calculated for more than two users. Moreover, we investigated the performance of the optimal MDFE using both IDMA (MDFE-IDMA) and CDMA (MDFE-CDMA) detectors. Generally, the MDE equalizer suffers from residual MAI interference effects at low signal-to-noise-ratios (SNR) due to the delay inherent in the convergence of the crossover filter taps. Therefore, a new decentralized multidimensional equalizer has been proposed to IDMA detector. Within design of decentralized equalizer, the convergence problem has been resolved by replacing the crossover filters with parallel interference canceler (PIC) for removing MAI dispersion. The proposed decentralized multidimensional equalizer shows a higher efficiency in removing MAI interference when compared with existing receivers in the literature. However, this is achieved at the expense of higher computational complexity compared to centralized multidimensional equalization.
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Rice, Michael, and Ed Satorius. "A COMPARISON OF MMSE AND CMA EQUALIZATION TECHNIQUES FOR ARTM TIER-1 WAVEFORMS." International Foundation for Telemetering, 2004. http://hdl.handle.net/10150/605053.
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International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, CaliforniaThe performance of two adaptive equalization techniques applicable to ARTM Tier-1 waveforms over a frequency selective multipath channel is summarized. Adaptive equalization based on the constant modulus algorithm (CMA) and the decision-directed minimum mean squared error (DF-MMSE) concept are shown to be effective in reducing the bit error rate in the presence of frequency selective multipath interference. The performance of the DF-MMSE equalizer is slightly better than the CMA equalizer. Implementation trade-offs between the two types of equalizers are also discussed.
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Kellar, Thomas W. "Cognitive Stimulation for Long-Term Care Adults with Dementia." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1410464307.
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Koch, H. J., K. Gurtler, and A. Szecsey. "Correlation of MMSE, SKT and clock test scores in patients with mild and moderate dementia." Nagoya University School of Medicine, 2005. http://hdl.handle.net/2237/5409.
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Mirbagheri, Arash. "Linear MMSE receivers for interference suppression & multipath diversity combining in long-code DS-CDMA systems." Thesis, Waterloo, Ont. : University of Waterloo, 2003. http://etd.uwaterloo.ca/etd/amirbagh2003.pdf.
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Thesis (Ph.D)--University of Waterloo, 2003."A thesis presented to the University of Waterloo in fulfilment of the thesis requirement for the degree of Doctor of Philosophy in Electrical and Computer Engineering". Includes bibliographical references. Also available in microfiche format.
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Foerster, Jeffrey Ronald. "The performance of matched-filter and MMSE receivers for DS-CDMA systems in multipath fading channels /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9908495.
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Nilsson, Molly. "Effekten av donepezil vid mild-måttlig Alzheimers sjukdom mätt med Mini mental state exam." Thesis, Linnéuniversitetet, Institutionen för kemi och biomedicin (KOB), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-51967.
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Alzheimer´s disease (AD) is today the world’s most common disease within dementia as it affects most number of people that are demented. There are no cure to AD, just symptomatic treatment are available. Scientists are still discussing the reason behind AD and many different theories exist. The most popular one is the amyloid cascade hypothesis. To diagnose AD many different types of scales are used to determine a person´s cognitive skills, also blood- and spinal cord samples are taken. One of the most popular scale that is used to diagnose AD is named mini mental state exam (MMSE). MMSE consists of several domains including: orientation, reading, mental arithmetic, writing and figure copying. The maximum of points are 30 and a score of 24 or less indicates some type of dementia. Today acetylcholinesteraseinhibitors like donepezil, rivastigmine and galantamine are used to treat people with mild to moderate AD. People with severe AD are recommended treatment with a NMDA-receptor-antagonist, memantine. The result from this study includes a summary of results from five studies. All of them studied the effect of donepezil over time and three of them also studied donepezils effect compared to placebo. Patients that were included had mild- moderate AD and in one study they measured a continued treatment with donepezil. All studies measured the results with scales and tests, including MMSE, that assessed patient’s cognitive ability. The results showed that patients treated with donepezil had significantly improved their scores on the scale MMSE at the end of the studies compared from baseline in three studies. When compared with placebo patients treated with donepezil got significantly better scores on MMSE. These changes were small even if significantly proven. The conclusion of this work was that MMSE is not optimal for measuring changes in AD if the patient is treated with donepezil because of the small changes. MMSE have difficulties to detect the small changes (a change of ≤ 3 points) and therefore other scales and tests are in need. Donepezil showed a significantly improvement in the beginning of the studies but after a few weeks that improvement had decreased or disappeared. It could be in everyone´s favor to start medication in an early stage of the disease and then after a while make a new assessment of the patient’s health.
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Peacock, Matthew James McKenzie. "Random Matrix Theory Analysis of Fixed and Adaptive Linear Receivers." University of Sydney, 2006. http://hdl.handle.net/2123/985.
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Doctor of Philosophy (PhD)This thesis considers transmission techniques for current and future wireless and mobile communications systems. Many of the results are quite general, however there is a particular focus on code-division multiple-access (CDMA) and multi-input multi-output (MIMO) systems. The thesis provides analytical techniques and results for finding key performance metrics such as signal-to-interference and noise power ratios (SINR) and capacity. This thesis considers a large-system analysis of a general linear matrix-vector communications channel, in order to determine the asymptotic performance of linear fixed and adaptive receivers. Unlike many previous large-system analyses, these results cannot be derived directly from results in the literature. This thesis considers a first-principles analytical approach. The technique unifies the analysis of both the minimum-mean-squared-error (MMSE) receiver and the adaptive least-squares (ALS) receiver, and also uses a common approach for both random i.i.d. and random orthogonal precoding. The approach is also used to derive the distribution of sums and products of free random matrices. Expressions for the asymptotic SINR of the MMSE receiver are derived, along with the transient and steady-state SINR of the ALS receiver, trained using either i.i.d. data sequences or orthogonal training sequences. The results are in terms of key system parameters, and allow for arbitrary distributions of the power of each of the data streams and the eigenvalues of the channel correlation matrix. In the case of the ALS receiver, we allow a diagonal loading constant and an arbitrary data windowing function. For i.i.d. training sequences and no diagonal loading, we give a fundamental relationship between the transient/steady-state SINR of the ALS and the MMSE receivers. We demonstrate that for a particular ratio of receive to transmit dimensions and window shape, all channels which have the same MMSE SINR have an identical transient ALS SINR response. We demonstrate several applications of the results, including an optimization of information throughput with respect to training sequence length in coded block transmission.
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Venkatasubramanian, Ramasamy. "Beamforming for MC-CDMA." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/31287.
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Orthogonal Frequency Division Multiplexing (OFDM) has recently gained a lot of attention and is a potential candidate for Fourth Generation (4G) wireless systems because it promises data rates up to 10Mbps. A variation of OFDM is Multi-Carrier CDMA (MC-CDMA) which is an OFDM technique where the individual data symbols are spread using a spreading code in the frequency domain. The spreading code associated with MC-CDMA provides multiple access technique as well as interference suppression.
Often times in cellular and military environments the desired signal can be buried below interference. In such conditions, the processing gain associated with the spreading cannot provide the needed interference suppression. This research work investigates multi-antenna receivers for OFDM and MC-CDMA systems; specifically this works investigates adaptive antenna algorithms for MC-CDMA for very different channel conditions. Frequency domain beamforming is studied in this research predominantly through simulation. As an alternative a time domain beamforming is also studied.
Time variations in the channel can disrupt the orthogonality between subcarriers. Minimum Mean Square Error (MMSE) detection coupled with MMSE beamforming is proposed for time varying channels. Semi-analytic results are derived to study the Bit Error Rate (BER) performance. These results show significant performance improvement in the presence of interference. Joint MMSE weights in space and frequency is also investigated and semi-analytic results are derived to study their BER performance.Master of Science
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Peacock, Matthew James McKenzie. "Random Matrix Theory Analysis of Fixed and Adaptive Linear Receivers." Thesis, The University of Sydney, 2005. http://hdl.handle.net/2123/985.
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This thesis considers transmission techniques for current and future wireless and mobile communications systems. Many of the results are quite general, however there is a particular focus on code-division multiple-access (CDMA) and multi-input multi-output (MIMO) systems. The thesis provides analytical techniques and results for finding key performance metrics such as signal-to-interference and noise power ratios (SINR) and capacity. This thesis considers a large-system analysis of a general linear matrix-vector communications channel, in order to determine the asymptotic performance of linear fixed and adaptive receivers. Unlike many previous large-system analyses, these results cannot be derived directly from results in the literature. This thesis considers a first-principles analytical approach. The technique unifies the analysis of both the minimum-mean-squared-error (MMSE) receiver and the adaptive least-squares (ALS) receiver, and also uses a common approach for both random i.i.d. and random orthogonal precoding. The approach is also used to derive the distribution of sums and products of free random matrices. Expressions for the asymptotic SINR of the MMSE receiver are derived, along with the transient and steady-state SINR of the ALS receiver, trained using either i.i.d. data sequences or orthogonal training sequences. The results are in terms of key system parameters, and allow for arbitrary distributions of the power of each of the data streams and the eigenvalues of the channel correlation matrix. In the case of the ALS receiver, we allow a diagonal loading constant and an arbitrary data windowing function. For i.i.d. training sequences and no diagonal loading, we give a fundamental relationship between the transient/steady-state SINR of the ALS and the MMSE receivers. We demonstrate that for a particular ratio of receive to transmit dimensions and window shape, all channels which have the same MMSE SINR have an identical transient ALS SINR response. We demonstrate several applications of the results, including an optimization of information throughput with respect to training sequence length in coded block transmission.
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Riedel, Oliver, Jens Klotsche, Annika Spottke, Günther Deuschl, Hans Förstl, Fritz Henn, Isabella Heuser, et al. "Cognitive impairment in 873 patients with idiopathic Parkinson’s disease." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-105332.
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Background: Parkinson’s disease (PD) is often accompanied by non-motor complications, such as dementia, depression, and psychotic symptoms, which worsen the prognosis and increase the personal and socioeconomic burden of disease. Prevalence estimates of these complications are quite variable and are lacking for the outpatient care sector.
Methods: As part of a larger, nationwide, cross-sectional epidemiological study in n=315 neurological outpatient settings in Germany, this paper estimates the frequency of dementia and cognitive impairment in n=873 outpatients meeting the UK Brain Bank criteria for idiopathic PD. Assessments were based on a clinical interview and neuropsychological assessments, including the Hoehn & Yahr rating and Unified Parkinson’s Disease Rating Scale (UPDRS). Cognitive impairment was assessed by the Mini-Mental State Exam (MMSE), Clock Drawing Test (CDT) and the Parkinson Neuropsychometric Dementia Assessment (PANDA) and the clinician’s diagnosis of dementia was based on the diagnostic criteria of DSMIV. Results Using standardized cutoff scores, the prevalence of cognitive impairment in the study sample as measured by various methods was 17.5% by MMSE (≤ 24), 41.8% by CDT (≥ 3), 43.6% by PANDA (≤ 14), and 28.6% met the DSM-IV criteria for dementia. All estimates increased with age and PD severity. Gender was an inconsistent contributor while illness duration had no significant impact on cognition. Multiple regression analyses revealed PD severity to be the strongest predictor of dementia risk (OR=4.3; 95 % CI: 2.1–9.1), while neuropsychiatric syndromes had independent, although modest additional contributions (OR=2.5, 95% CI: 1.6–3.8).
Conclusion: Estimates of cognitive impairment and dementia in PD patients are largely dependent on the diagnostic measure used. Using established clinical diagnostic standards for dementia the overall rate on routine outpatient neurological care is 28.6%, but using more sensitive neuropsychological measures, rates for cognitive impairment might be up to 2-fold higher. The MMSE revealed strikingly low sensitivity. Neuropsychiatric syndromes, in addition to PD severity and age, have an independent – although modest – additional contribution to patients’ risk for cognitive impairment and dementia.
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FERRERO, THERESE. "Taux de declin des fonctions cognitives mesure par le mmse d'une population hospitalisee demente et non demente." Paris, 1991. http://www.theses.fr/1991PA05C122.
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Riedel, Oliver, Jens Klotsche, Annika Spottke, Günther Deuschl, Hans Förstl, Fritz Henn, Isabella Heuser, et al. "Cognitive impairment in 873 patients with idiopathic Parkinson’s disease: Results from the German Study on Epidemiology of Parkinson’s Disease with Dementia (GEPAD)." Technische Universität Dresden, 2008. https://tud.qucosa.de/id/qucosa%3A26582.
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Background: Parkinson’s disease (PD) is often accompanied by non-motor complications, such as dementia, depression, and psychotic symptoms, which worsen the prognosis and increase the personal and socioeconomic burden of disease. Prevalence estimates of these complications are quite variable and are lacking for the outpatient care sector.
Methods: As part of a larger, nationwide, cross-sectional epidemiological study in n=315 neurological outpatient settings in Germany, this paper estimates the frequency of dementia and cognitive impairment in n=873 outpatients meeting the UK Brain Bank criteria for idiopathic PD. Assessments were based on a clinical interview and neuropsychological assessments, including the Hoehn & Yahr rating and Unified Parkinson’s Disease Rating Scale (UPDRS). Cognitive impairment was assessed by the Mini-Mental State Exam (MMSE), Clock Drawing Test (CDT) and the Parkinson Neuropsychometric Dementia Assessment (PANDA) and the clinician’s diagnosis of dementia was based on the diagnostic criteria of DSMIV. Results Using standardized cutoff scores, the prevalence of cognitive impairment in the study sample as measured by various methods was 17.5% by MMSE (≤ 24), 41.8% by CDT (≥ 3), 43.6% by PANDA (≤ 14), and 28.6% met the DSM-IV criteria for dementia. All estimates increased with age and PD severity. Gender was an inconsistent contributor while illness duration had no significant impact on cognition. Multiple regression analyses revealed PD severity to be the strongest predictor of dementia risk (OR=4.3; 95 % CI: 2.1–9.1), while neuropsychiatric syndromes had independent, although modest additional contributions (OR=2.5, 95% CI: 1.6–3.8).
Conclusion: Estimates of cognitive impairment and dementia in PD patients are largely dependent on the diagnostic measure used. Using established clinical diagnostic standards for dementia the overall rate on routine outpatient neurological care is 28.6%, but using more sensitive neuropsychological measures, rates for cognitive impairment might be up to 2-fold higher. The MMSE revealed strikingly low sensitivity. Neuropsychiatric syndromes, in addition to PD severity and age, have an independent – although modest – additional contribution to patients’ risk for cognitive impairment and dementia.
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Xu, Xin. "IEEE 802.11n MIMO Modeling and Channel Estimation Implementation." Thesis, Linköpings universitet, Institutionen för systemteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-81647.
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With the increasing demand of higher data rate for telecommunication, the IEEE802.11n standard was constituted in 2009. Themost important character of the standard is MIMO-OFDM, which not only improves the throughput but also the spectrumefficiency and channel capacity. This report focuses on the physical layer IEEE802.11n model. By utilizing an existingSimulink based IEEE802.11n system, functionalities like MIMO (up to 4*4), OFDM, STBC, Beamforming, and MMSEdetector are simulated. The results such as bit error rate, packet error rate and bit rate with different system settings are given.Furthermore, the channel estimation process is clarified, and a DSP builder based MMSE detector is realized, which can fulfillexactly the same function as the Simulink model.
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Nassr, Husam, and Kurt Kosbar. "PERFORMANCE EVALUATION FOR DECISION-FEEDBACK EQUALIZER WITH PARAMETER SELECTION ON UNDERWATER ACOUSTIC COMMUNICATION." International Foundation for Telemetering, 2017. http://hdl.handle.net/10150/626999.
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This paper investigates the effect of parameter selection for the decision feedback equalization (DFE) on communication performance through a dispersive underwater acoustic wireless channel (UAWC). A DFE based on minimum mean-square error (MMSE-DFE) criterion has been employed in the implementation for evaluation purposes. The output from the MMSE-DFE is input to the decoder to estimate the transmitted bit sequence. The main goal of this experimental simulation is to determine the best selection, such that the reduction in the computational overload is achieved without altering the performance of the system, where the computational complexity can be reduced by selecting an equalizer with a proper length. The system performance is tested for BPSK, QPSK, 8PSK and 16QAM modulation and a simulation for the system is carried out for Proakis channel A and real underwater wireless acoustic channel estimated during SPACE08 measurements to verify the selection.
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羽多野, 裕之, 敬也 山里, 啓. 岡田, and 正昭 片山. "レーダネットワークにおけるMMSEを用いた障害物の位置推定." 電子情報通信学会, 2005. http://hdl.handle.net/2237/12724.
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Pop, Alina Boivin Jean-Marc. "Pertinence du MMSE chez le patient hypertendu en médecine générale analyse à partir des patients de l'étude ADELAHYDE /." [S.l.] : [s.n.], 2008. http://www2.scd.uhp-nancy.fr/docnum/SCDMED_T_2008_POP_ALINA.pdf.
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Gao, Jason. "Equalisation for carrierless amplitude and phase modulation." Thesis, Curtin University, 2002. http://hdl.handle.net/20.500.11937/233.
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Carrierless amplitude and phase (CAP) modulation is generally regarded as a bandwidth efficient two-dimensional (2-D) passband line code. It is closely related to the pulse amplitude modulation (PAM) and quadrature amplitude modulation (QAM) schemes. CAP has been proposed for various digital subscriber loop (DSL) systems over unshielded twisted pairs of copper wires. In this thesis, our main focus is on the minimum mean-square error (MMSE) performance of the ideal (i.e., infinite length) linear and non-linear (decision feedback) CAP receivers/equalisers in the presence of additive, coloured Gaussian noise, and/or data-like cross-talks. An in-depth analysis is given on the performance of both receiver structures. In the case of the linear receiver, one possible view of the overall CAP transceiver system which includes both data and cross-talk transmission paths is that it is a linear multiple-input multiple-output (MIMO) system. Accordingly, the existing MMSE results for a general MIMO system are applicable also to CAP systems. However, up to date, this approach was shown to be unsuccessful in the sense that the derived MMSE expressions are too complex and offer little insights. In our analysis, in order to find a more incisive MMSE expression, we reconsider the problem of minimisation of the MSEs at slicers. By exploiting the Hilbert transform pair relationship between the impulse responses of the inphase and quadrature transmit shaping filters, we are able to obtain an elegant and more meaningful MMSE expression, as well as the corresponding transfer functions of the optimum linear receive filters. In the case of the nonlinear, or decision feedback equaliser (DFE), receiver, we start our analysis with the receiver structure of a generic multidimensional (>/= 3) CAP-type system.This receiver consists of a bank of analog receive filters, the number of which equals the dimension of the CAP line code, and a matrix of cross-connected, infinite-length, baud-spaced feedback filters. It is shown that the optimum filters and the corresponding MMSE of the DFE receiver require the factorisation of a discrete-time channel spectral matrix. This mathematically intractable step can be avoided, however, when the DFE results are specialised to a standard 2-D CAP system where we are able to again exploit the Hilbert transform pair relationship to derive a further and more useful MMSE expression. Three sets of numerical studies are given on the MMSE performance of the CAP receivers. In the first set of studies. we model the sum of all crosstalks as an additive, Gaussian noise source and select three test transmission channels over which we compare the MMSE performance of the linear and DFE receiver structures. In the second set of studies, we compare the performance of the two receiver structures, but in a data-like cross-talk environment. The results demonstrate the importance of NEXT equalisation in the design of CAP receivers operating in a NEXT dominant environment. In the final set of studies which follows from the second set of studies, we investigate the relationship between the MMSE performance of the DFE receiver and system parameters which include excess bandwidth, data rate, CAP scheme. and relative phase between the received signal and the NEXT signal. The results show that data-like cross-talks can be effectively suppressed by using a large excess bandwidth (alpha > 1 in the case of a RC transmit shaping filter) alone.The relative phase also affect; the receiver performance. but to a lesser degree. In addition to the MMSE performance analysis. implementation issues of an adaptive linear CAP receiver are also considered. We propose a novel linear receiver by appending two fixed analog filters to the front-end of the existing adaptive linear receiver using fractionally-spaced equalisers (FSE). We show that if the analog filters are matched to the transmit shaping filters, then inphase and quadrature finite-length FSEs in the proposed receiver have the same NINISE solution. We further propose a modified least-mean-square (LMS) algorithm which takes advantage of this feature. The convergence analysis of the proposed LMS algorithm is also given. We show that the modified LMS algorithm converges approximately twice as fast as the standard LMS algorithm, given the same misadjustment, or alternatively, it halves the misadjustment, given the same initial convergence rate.
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Jönsson, Marie. "Aktivitetsförmåga, kognitiv funktion samt risk för trycksår, undernäring och fall : - äldre personer med återinläggning inom medicinsk akut slutenvård." Thesis, Örebro universitet, Institutionen för hälsovetenskap och medicin, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-29550.
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Righi, Vitor Angelo Pozzatti. "ALGORITMO DE LOCALIZAÇÃO UTILIZANDO O MÉTODO MMSE PARA O CÁLCULO DE POSIÇÃO DE NÓS SENSORES EM UMA REDE MÓVEL." Universidade Federal de Santa Maria, 2013. http://repositorio.ufsm.br/handle/1/5437.
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Conselho Nacional de Desenvolvimento Científico e TecnológicoApplications that use sensor networks depends on knowing which position where each node is arranged in a particular geographic area. For this, there are algorithms that perform location calculations to estimate the exact position of each node. These algorithms use a different techniques and metrics to make it, for example: the measure of intensity of signal transmission between two nodes. In a sensor network with high density, it becomes infeasible to manually configuring each node positioning. To optimize this task, was developed different types of localization algorithms, with application in several areas, such as tracking, routing protocols, network density control, self organizing, monitoring remote areas, precision agriculture, among others. The basis for localization algorithms is to have a number of reference points, where from these, is calculated the position of each node. A network of sensors with a greater number of reference points, one can consider a network with higher accuracy for calculating the position of its nodes. This is due to being closer to the reference points. However, may result in a higher processing, thereby having a higher energy consumption. Developing a location algorithm with fewer reference points is not a trivial problem. This, because will increase the distance between the node and the reference point and may thereby inserting errors in the measurement of the criteria for the calculation of positioning. For calculation purposes, there are two types of algorithms, algorithms for centralized processing and distributed processing algorithms. Each with its advantages and disadvantages that will be discussed in this paper. The location algorithm is based on a calculation according to data coordinates in a coordinate system, which is raised according to the technique used to denote the distance between the sensor node and the reference points. The importance of knowing the location of each node, there is the need to know exactly where a particular event is occurring. For example, a forest that occupies a large geographic area is to principles of fire at different locations.
Aplicações que utilizam redes de sensores dependem de saber qual a posição onde cada nó encontra-se disposto em uma determinada área geográfica. Para isto, existem algoritmos de localização que efetuam cálculos a fim de estimar a posição exata de cada nó. Estes algoritmos utilizam-se de diferentes técnicas e medidas para realizar tal tarefa, como por exemplo: a medida de intensidade de sinal de transmissão entre dois nós. Em uma rede de sensores com alta densidade, torna-se inviável a configuração manual do posicionamento de cada nó. Para otimizar esta tarefa, foram desenvolvidos diferentes tipos de algoritmos de localização, com aplicação nas mais diversas áreas, como: rastreamento, protocolos de roteamento, controle de densidade da rede, auto organização, monitoramento de áreas remotas, agricultura de precisão, entre outros. A base para algoritmos de localização é possuir um número de pontos de referência, onde a partir destes, será calculado a posição de cada nó. Uma rede de sensores com maior número de pontos de referência, pode-se considerar uma rede com maior precisão para o cálculo de posição de seus nós. Isso, é devido aos nós estarem mais próximos aos pontos de referência. Porém, pode acarretar em um maior processamento, assim, tendo um maior consumo de energia. Projetar um algoritmo de localização com um menor número de pontos de referência não é um problema trivial. Isto porque irá aumentar a distância entre o nó e o ponto de referência, podendo desta forma, inserir erros na medição dos critérios para o cálculo de posicionamento. Para fins de cálculo, existem dois tipos de algoritmos, os algoritmos de processamento centralizado e os algoritmos de processamento distribuído. Cada um com suas vantagens e desvantagens que serão abordadas no decorrer deste trabalho. O algoritmo de localização baseia-se em um cálculo de acordo com as coordenadas em um dado sistema de coordenadas, que será levantada de acordo com a técnica utilizada para estipular a distância entre o nó sensor e os pontos de referência. A importância de conhecer a localização de cada nó, dá-se a necessidade de saber exatamente onde está ocorrendo determinado evento. Por exemplo, uma floresta que ocupa uma grande área geográfica está com princípios de incêndio em diferentes locais. É preciso avaliar quais são estes locais e qual significa um maior risco de destruição, para isto, é preciso saber a posição exata de cada local e assim tomar as devidas decisões de qual princípio deverá ser combatido primeiro. Neste caso, os nós sensores estariam estáticos, porém seria uma rede de sensores de alta densidade para cobrir uma área significativa de floresta. Pode-se também ter uma rede de sensores com nós móveis, onde então o objetivo é realizar o rastreamento da locomoção destes nós. A partir deste rastreamento, pode-se identificar o comportamento de um rebanho de animais por exemplo, verificando seu deslocamento, velocidade e direção. Com estes dados de comportamento, dependendo do animal pode-se deduzir se ele está doente, alimentando-se ou até mesmo morto se imóvel por um longo período de tempo.
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Au, Chun-lam Antony, and 歐浚林. "Comparision between volumetric and DKI parametric analyses of hippocampus for correlations with MMSE scores in patients with Alzheimer's disease." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/193547.
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Volumetric analysis (VA) in magnetic resonance imaging (MRI) has provided great comprehension of the neuroanatomical changes associated to normal cognition and progression from mild cognitive impairment (MCI) to Alzheimer’s disease (AD), the most common form of dementia. However, the use of VA has primarily focused in gray matter changes; the emergence of diffusion tensor imaging (DTI) has allowed a better understanding of the microstructural changes in both white and gray matters in MCI and AD patients, with numerous studies showing DTI to be more sensitive than VA in discriminating between MCI to AD.
Diffusion kurtosis imaging (DKI), an extension of DTI, is speculated to be more sensitive in detecting changes due to differences in mathematical modeling, as it accounts for non-Gaussian diffusion in the brain. Studies using DKI suggested kurtosis parameters—axial, radial, and mean kurtoses—are able to provide further microstructural details in additional information to tensor and diffusion parameters, namely axial, radial, and mean diffusivities, and fractional anisotropy. In this study, DKI is compared to DTI and VA in an attempt to evaluate the sensitivities of each technique.
DKI of all four cerebral lobes and VA of the hippocampus were performed in 30 patients, 18 diagnosed with AD and 12 with MCI. Mann-Whitney U test was performed to determine differences between MCI and AD, and correlations between diffusion parameters and hippocampal volume to mini-mental state examination (MMSE) scores as a biomarker of cognitive function were tested using Pearson’s R correlation test.
MMSE scores were statistically different between sexes (p = 0.025) and between MCI and AD groups (p = 0.048), as well as positively correlated with age (p = 0.004). A marginal trend was observed in the hippocampal volume between MCI and AD (p = 0.077), and did not significantly correlate with MMSE. Several diffusivity and kurtosis parameters were significantly different between MCI and AD groups in the white and gray matters of the parietal and occipital lobes. Only tensor parameters had significant negative correlations with MMSE scores in within-group analyses of the two lobes. Correlational tests of white and gray matters of all four lobes to MMSE scores revealed more significant correlations between tensor parameters than kurtosis parameters.
Findings from the present study provide further evidence that diffusion MRI is a more sensitive technique than VA in the discrimination between MCI and AD. Results from this study also corroborate with another DKI study exploring diffusivity in neuroanatomical regions predominately composed of white matter in AD progression. While DKI provides additional information on the microstructural changes of white matter and gray matter during disease progression in the brain, whether DKI is superior to DTI requires further research. Diffusion MRI appears to be more advantageous when comparing cognitive function on a continuum like MMSE scores than segregated groups.published_or_final_version
Diagnostic Radiology
Master
Master of Medical Sciences
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Zhi-Wei, Kang, and 康志偉. "A Group MMSE for Multiuser Detector." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/15635471461722385370.
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碩士國立臺北科技大學
電機工程系碩士班
90
The goal of this thesis is to research into multi-user detector (MUD) technology on DS-CDMA system and improve entire performance of the system. In order to reduce the complexity and increase the practicability, we consider using a new MUD receiver which is called the Group MMSE multi-user detector (GMMSE-MUD). This receiver will firstly divide all of the users into groups, then detects the users in each group using the MMSE theory. Instead of the number of all these users in MMSE-MUD, the complexity of this model depends only on the number of the users in each group. Therefore the new model can reduce the complexity of the system accordingly. In order to further improve the system’s performance and reduce the bit error rate, we can combine the GMMSE with SIC or PIC. The performance of this system is very close to performance of the MMSE-MUD receiver. In this thesis, we analyze effect of the performance in grouping method. And we also investigate performance of GMMSE multi-user detector in the synchronous, asynchronous and multi-path environment.
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Gaffar, Mohammed Yusuf Abdul. "MMSE equalizers and precoders in turbo equalization." Thesis, 2003. http://hdl.handle.net/10413/4155.
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Transmission of digital information through a wireless channel with resolvable multipaths or a bandwidth limited channel results in intersymbol interference (1SI) among a number of adjacent symbols. The design of an equalizer is thus important to combat the ISI problem for these types of channels and hence provides reliable communication. Channel coding is used to provide reliable data transmission by adding controlled redundancy to the data. Turbo equalization (TE) is the joint design of channel coding and equalization to approach the achievable uniform input information rate of an ISI channel. The main focus of this dissertation is to investigate the different TE techniques used for a static frequency selective additive white Gaussian noise (AWGN) channel. The extrinsic information transfer (EXIT) chart is used to analyse the iterative equalization/decoding process and to determine the minimum signal to noise ratio (SNR) in order to achieve convergence. The use of the Minimum Mean Square Error (MMSE) Linear Equalizer (LE) using a priori information has been shown to achieve the same performance compared with the optimal trellis based Maximum A Posterior (MAP) equalizer for long block lengths. Motivated by improving the performance of the MMSE LE, two equalization schemes are initially proposed: the MMSE Linear Equalizer with Extrinsic information Feedback (LE-EF (1) and (U)). A general structure for the MMSE LE, MMSE Decision Feedback Equalizer (DFE) and two MMSE LE-EF receivers, using a priori information is also presented. The EXIT chart is used to analyse the two proposed equalizers and their characteristics are compared to the existing MAP equalizer, MMSE LE and MMSE DFE. It is shown that the proposed MMSE LE-EF (1) does have an improved performance compared with the existing MMSE LE and approaches the MMSE Linear Equalizer with Perfect Extrinsic information Feedback (LE-PEF) only after a large number of iterations. For this reason the MMSE LE-EF is shown to suffer from the error propagation problem during the early iterations. A novel way to reduce the error propagation problem is proposed to further improve the performance of the MMSE LE-EF (I). The MAP equalizer was shown to offer a much improved performance over the MMSE equalizers, especially during the initial iterations. Motivated by using the good quality of the MAP equalizer during the early iterations and the hybrid MAP/MMSE LE-EF (l) is proposed in order to suppress the error propagation problem inherent in the MMSE LE-EF (I). The EXIT chart analysis reveals that the hybrid MAP/MMSE LE-EF (l) requires fewer iterations in order to achieve convergence relative to the MMSE LE-EF (l). Simulation results demonstrate that the hybrid MAP/MMSE LE-EF (I) has a superior performance compared to the MMSE LE-EF (I) as well as approaches the performance of both the MAP equalizer and MMSE LE-PEF at high SNRs, at the cost of increased complexity relative to the MMSE LEEF (I) receiver. The final part of this dissertation considers the use of precoders in a TE system. It was shown in the literature that a precoder drastically improves the system performance. Motivated by this, the EXIT chart is used to analyse the characteristics of four different precoders for long block lengths. It was shown that using a precoder results in a loss in mutual information during the initial equalization stage. However" we show by analysis and simulations that this phenomenon is not observed in the equalization of all precoded channels. The slope of the transfer function, relating to the MAP equalization of a precoded ISI channel (MEP), during the high input mutual information values is shown to play an important role in determining the convergence of precoded TE systems. Simulation results are presented to show how the precoders' weight affects the convergence of TE systems. The design of the hybrid MAP/MEP equalizer is also proposed. We also show that the EXIT chart can be used to compute the trellis code capacity of a precoded ISI channel.Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.
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Chia, Hung Tsai, and 蔡佳宏. "Hybrid MMSE and SIC for Multiuser Detection." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/97084058668270918427.
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碩士國立臺灣科技大學
電子工程系
89
Near-far problem limits both of the system performance and the overall network capacity in the reverse link of a DS-CDMA system. For this, various approaches have been addressed, to overcome these difficulties, among which the multiuser detection (MUD) has been proved to be effective. Multi-user detection (MUD) has demonstrated to be an effective approach to resolve this problem. The optimal MUD, however, in general calls for substantial computational overhead. As such, some suboptimal ones, such as minimum mean-squared error (MMSE) MUD and successive interference cancellation (SIC) MUD, are of more practical interests. Nevertheless the computational complexity of the MMSE MUD is still high, while the SIC MUD suffers the latency problem for the detection of the weakest signals. In light of this, this thesis proposes a hybrid MMSE and SIC MUD which possesses the advantage of both detection schemes, but with alleviated aforementioned drawbacks. The approach first divides the users into several groups with each group consisting of users with a close power level. The SIC MUD is then used to distinguish users among different groups, while the MMSE MUD is used to detect users within each group. As such, the computational complexity of the MMSE MUD and the latency problem in the SIC MUD can thus be greatly mitigated. Besides, since the SIC MUD substrates the reconstructed signal from the original one stage by stage, the reconstructed error can then propagate and eventually may destroy to detection process. To overcome this, this thesis also addresses a new dynamic mapping function following the MMSE MUD carried out in each group of the proposes hybrid approach. This new mapping function can not only alleviate the false alarm induced in the reconstruction process, but also possesses dynamic adjusting scheme according to the signal characteristic. Furnished simulations show that the new approach outperforms both of the traditional MMSE MUD and SIC MUD algorithms.
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Datta, Gupta Syamantak. "On MMSE Approximations of Stationary Time Series." Thesis, 2013. http://hdl.handle.net/10012/8143.
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In a large number of applications arising in various fields of study, time series are approximated using linear MMSE estimates. Such approximations include finite order moving average and autoregressive approximations as well as the causal Wiener filter. In this dissertation, we study two topics related to the estimation of wide sense stationary (WSS) time series using linear MMSE estimates.
In the first part of this dissertation, we study the asymptotic behaviour of autoregressive (AR) and moving average (MA) approximations. Our objective is to investigate how faithfully such approximations replicate the original sequence, as the model order as well as the number of samples approach infinity. We consider two aspects: convergence of spectral density of MA and AR approximations when the covariances are known and when they are estimated. Under certain mild conditions on the spectral density and the covariance sequence, it is shown that the spectral densities of both approximations converge in L2 as the order of approximation increases. It is also shown that the spectral density of AR approximations converges at the origin under the same conditions. Under additional regularity assumptions, we show that similar results hold for approximations from empirical covariance estimates.
In the second part of this dissertation, we address the problem of detecting interdependence relations within a group of time series. Ideally, in order to infer the complete interdependence structure of a complex system, dynamic behaviour of all the processes involved should be considered simultaneously. However, for large systems, use of such a method may be infeasible and computationally intensive, and pairwise estimation techniques may be used to obtain sub-optimal results. Here, we investigate the problem of determining Granger-causality in an interdependent group of jointly WSS time series by using pairwise causal Wiener filters. Analytical results are presented, along with simulations that compare the performance of a method based on finite impulse response Wiener filters to another using directed information, a tool widely used in literature. The problem is studied in the context of cyclostationary processes as well. Finally, a new technique is proposed that allows the determination of causal connections under certain sparsity conditions.
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Chao, Soul-Yu, and 趙守毓. "Power Control with Adaptive MMSE Interference Suppression." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/91436470475820613049.
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碩士國立交通大學
電信工程系
91
The direct-sequence code division multiple access (DS/CDMA) transmission technique has been widely investigated and used in practical wireless communication system. In this thesis, MMSE interference suppression combined with adaptive power control is investigated. This method achieves the users’ target SIR with the minimum total transmitted power. Four adaptive MMSE interference suppression algorithms are discussed, so are their adaptive power control methods. In Rayleigh fading channel, conventional recursive least square (RLS) algorithm cannot converge easily under fast time variation. The differential least square (DLS) algorithm that adopts differential encoding and another error function can overcome the problem. The SIR of interference suppression filter output and channel parameter must be estimated in adaptive power control combined with DLS algorithm. We propose a channel estimation method based on DLS algorithm that doesn’t need extra computations and just takes time average over the interference suppression filter output. The SIR of filter output will be acquired through the method of channel estimation. We have used the computer to simulate adaptive power control combined with DLS interference suppression in flat Rayleigh fading channel.
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Tseng, Hsien-Sheng, and 曾憲聖. "Blind Zero-Forcing Equalization Based on MMSE Criterion." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/68071510473903930432.
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碩士中原大學
電子工程研究所
92
Blind channel identification and equalization become important and popular in digital communication system. Since T. Kailath et al have proposed the algorithms utilizing the cyclostationary signal via oversampling the received signals or receiving signals by antenna arrays. A number of blind equalization methods based on SIMO system model and second order statistics of channel output have been developed. In this paper, we derive a new algorithm for blind equalization based on zero-forcing condition and minimum mean square error criterion. Minimizing the mean square error based on the different delay equalizers’ output . All possible delay zero-forcing equalizers can be computed simultaneously without channel coefficients matrix estimation so that the influence of the channel identification is reduced. Simulations are presented to demonstrate adequate performance of the new blind equalization algorithm.
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Liu, G. S., and 劉吉祥. "Linear Prediction Methods for Direct Blind MMSE Equalization." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/88904630936744020987.
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碩士國立交通大學
電信工程系
89
The channel equalization using the high-order statistics methods has a slow convergence rate. In recent years, the second-order statistics (SOS) methods have become a popular research. One of the SOS methods, such as the Ding algorithm proposed by Ding in 2000 is an advanced type of outer-product decomposition algorithm (OPDA), has been shown to have better performance than many existing algorithms. But Ding algorithm needs the pseudo-inverse of the correlation matrix, thus the computation is not simple and could cause numerical problems. It is also not suit for tracking time-varying channels. By the use of linear prediction (LP) method proposed by Fan, we deduce a new algorithm based on Ding algorithm. We name the new algorithm as linear prediction based outer-product decomposition algorithm (LP-OPDA). LP-OPDA combines both the advantages of LP and Ding algorithm and has its new advantages. LP-OPDA does not need the pseudo-inverse operation, thus have superior performance over Ding algorithm. LP-OPDA is available for tracking time-varying channels and also computationally efficient. From the simulation results, we can see LP-OPDA has superior performance over Ding algorithm and many other existing algorithms in many ways.
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wei, Li che, and 利哲瑋. "Adaptive Unbiased MMSE Algorithm for Error Rate Improvement." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/15628097402548234572.
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碩士淡江大學
電機工程學系
92
We derive a generalized expression of the error probability for an unbiased linear equalizer with infinite length in an M-ary PAM channel. We then show the Saltzberg bound for an unbiased linear equalizer with finite length in an M-ary PAM channel. Using the error probability expression for the infinite length equalizer and the Saltzberg bound for the finite length equalizer, we develop an adaptive unbiased minimum mean square error(AUMMSE) algorithm to effectively improve error probability performance. In addition to the error probability improvement, we also find that our AUMMSE algorithm offers much better convergence behavior than the conventional least mean square(LMS) algorithm for realizing MMSE. The AUMMSE learning curves give much smoother and faster convergence as compared to LMS.
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Lee, Chia En, and 李佳恩. "Feasibility of Testing MMSE Scale with Technology Interface." Thesis, 2019. http://ndltd.ncl.edu.tw/cgi-bin/gs32/gsweb.cgi/login?o=dnclcdr&s=id=%22107CGU05712005%22.&searchmode=basic.
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Lee, Da-Long, and 李達龍. "The Investigation of Filterbank OFDM Systems with MMSE Equalization." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/25724126503028662473.
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碩士國立中央大學
通訊工程研究所
93
In this thesis we investigate the use of the filterbank-based multicarrier communication system in the indoor environment. The filterbank-based system as opposed to DFT OFDM, is that the property of low sidelobe in filterbank can reduce intercarrier interference which is typically serious for some situations in OFDM. First, the choice of the filterbank design parameters is discussed. The receiver characteristics of different equalization structures are studied, and their complexity and performance are compared as well. Finally, the IEEE 802.11a OFDM system is compared with the filterbank-based multicarrier proposal. A quasi-static channel is used and the noise considers narrowband interference and AWGN. The results show that the performance of filterbank-based system is superior to the IEEE 802.11a OFDM system with the penalty of complexity and longer training sequence.
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Huang, Wan-Jen, and 黃婉甄. "FIR MIMO MMSE-DFE Structures and Fast Optimization Algorithm." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/65840423527379544154.
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碩士國立臺灣大學
電信工程學研究所
91
In multiple input multiple output (MIMO) wireless communication system, the received signals suffer not only noise and intersymbol interference (ISI) due to multipath propagation, but also interuser interference(IUI) due to simultaneous transmissions of several users. To eliminate this interference, we proposed three scenarios of MIMO MMSE-DFE in the receiver. The first scenario is the conventional MIMO MMSE-DFE. The second and third scenarios respectively apply the concepts of successive interference cancellation (SIC) and parallel interference cancellation (PIC). We also proposed a sorting algorithm for the second scenario to decrease error probability. It is shown that the performance of the second scenario with sorting or the third scenario is almost as good as the MAP estimation. The coefficients of the second scenario and third scenario can be obtained from the coefficients and error covariance matrix of the first scenario. We also proposed a fast algorithm for computing the inversion of a large matrix required in the optimization of scenario 1. It is an application of the generalized Schur algorithm and reduces the complexity from O(n3) to O(n2).
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Lo, Yu-Cheng, and 羅宇誠. "A Resource-Sharing Architecture for MMSE Linear Equalizer Designs." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/04780754233808816872.
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碩士國立清華大學
資訊工程學系
91
Almost all communication systems need to deal with the distortion problems due to the inter-symbol interference (ISI). This phenomenon occurs when a sequence of signals is transmitted through a bandlimited channel. Adjacent signal pulses may disperse and overlap with one another in time. To address this issue, proper filters are necessary at the transmitter end and/or the receiver end, requiring special techniques based on so-called Nyquist’s pulse-shaping criterion. Among them, the raised-cosine filter is one of the most widely used. In addition, equalization is another technique to combat ISI. Various algorithms for equalization have been proposed in the literature. In this thesis, Minimum Mean Square Error (MMSE) equalizer is adopted. We propose a cost-effective architecture to realize such an equalizer. The most difficult part of realizing an MMSE type of equalizer lies in the computation of the inverse of an auto-correlation matrix. Direct computation often consumes too much hardware. The contribution of this thesis is mainly a new architecture to implement the iterative process of Gauss-Seidel algorithm for inverse matrix computation. In this architecture, resource sharing is done in a way that the hardware utilization is dramatically improved, the target perform is achieved, while the design size is significantly reduced by 63% as compared to a naïve version. In summary, we use only five complex multipliers in this design to perform various tasks required in an equalizer such as the channel estimation, and the computation of auto-correlation matrix and the equalizer’s adaptive coefficients.
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Su, Wen-Shu, and 蘇文樹. "A MMSE Partial Parallel Interference Cancellator for Multiuser Detection." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/87786817476702576818.
Full textAbstract:
碩士國立交通大學
電信工程系
88
The parallel inteference cancellation (PIC) detector is an effective yet simple multiuser detector for code-division multiple access (CDMA) systems. The performance of the standard PIC can be further improved by the so called the partial PIC. For the received signal for a particular user, the partial PIC only partially cancels the interference regenerated from other users. The amount of cancellation is controlled by a partial cancellation factor. Previously, this factor is obtained by trial and error. No theoretic results were reported. In this thesis, we introduce a minimum mean square error (MMSE) criterion for the partial PIC. Based on this criterion, the closed-form solution is derived for the optimal cancellation factor. Simulations show that the optimal cancellation factor is very close to the one used in previous work. Also, the optimal factor is not sensitive to the noise level and the interferencing signal power.
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Chang, Kuang-Chun, and 張光君. "An improved MMSE-PIC method for iterative MIMO detection." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/78319468521517077564.
Full textAbstract:
碩士國立中正大學
通訊工程研究所
103
Iterative detection and decoding (IDD) for multiple-input-multiple-output communication systems has drawn great research interests lately as it can achieve near-capacity performance of the MIMO channel. While the maximum a-posteriori probability (MAP) detector can achieve the optimal performance, the required complexity is often prohibitive for practical implementation. In order to reduce the computational complexity in IDD, the minimum-mean-squared-error parallel interference cancellation (MMSE-PIC) detector has been proposed. The MMSE-PIC detector has the advantage of much lower computational complexity compared to the MAP detector but the error rate performance is much worse. In this thesis, we propose an improved MMSE-PIC detector by combining the MAP and MMSE-PIC detection. Simulation results show that the proposed detection scheme can achieve better error rate performance comparing to the MMSE-PIC detection while the computational complexity is still lower than that of the MAP detection.
45
李淑伶. "Quasi MMSE controller for dynamic run-to-run system." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/80856784085218081434.
Full text
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Thakadu, Batlhowahela C. D. "Lattice-structure based adaptive MMSE detectors for DS-CDMA systems." Thesis, 2001. http://hdl.handle.net/10413/5274.
Full textAbstract:
There has been significant interest in the research community on detectors for DS-CDMA
systems. The conventional detector, which detects users ' data bits, by using a filter matched to the
users' spreading codes, has two major drawbacks. These drawbacks are (1) its capacity is limited
by multiple access interference (MAl) and (2) it suffers from the near-far problem. The remedy to
these problems is to use a multiuser detector, which exploits knowledge of users ' transmission
and channel parameters to mitigate MAl. Such detectors are called multi user detectors (MUD). A
number of these detectors have been proposed in the literature. The first such detector is the
optimal detector proposed by Verdu. Following Verdu's work a number of suboptimal detector
were proposed. These detectors offer better computational complexity at the expense of the bit
error rate performance. Examples of these detectors are the decorrelating detector, the minimum
mean squared error detector (MMSE), the successive interference cancellation and parallel
interference cancellation. In this thesis, we consider the adaptive DS-CDMA MMSE detector,
where lattice-based filter algorithms are employed to suppress MAl. Most of the work in the
literature has considered the implementation of this detector using the Least Mean Square (LMS)
algorithm. The disadvantage of using the LMS algorithm to implement the MMSE detector is that
the LMS algorithm converges very slowly.
The main aims of this thesis are as follows. A review of the literature on MUD is presented. A
lattice based MUD is then proposed and its performance evaluated using both simulation and
analytical methods. The results obtained are compared with those of the LMSMMSE detector.
From the results obtained the adaptive Lattice-MMSE detector is shown to offer good
performance tradeoff between convergence results and BER results.Thesis (M.Sc.Eng.)-University of Natal, Durban, 2001.
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Huang, Wenjie. "Widely Linear MIMO MMSE Filter and Joint MLSE for VAMOS." Thesis, 2010. http://hdl.handle.net/10012/5577.
Full textAbstract:
Currently, the 3rd Generation Partnership Project (3GPP) standards body is working actively to specify Voice services over Adaptive Multi-user channels on One Slot (VAMOS), an enhanced transmission scheme to double the voice service capacity in existing Global System for Mobile communications (GSM) system. Capacity increase is achieved by multiplexing two users in the same timeslot within the same radio frequency channel. With this new transmission scheme, several characteristics of VAMOS downlink signals can be taken into account in mobile station equalizer design. Firstly, the base station maps a pair of bits from the two VAMOS users to a quaternary symbol whose I/Q amplitude ratio may vary burst by burst. When the ratio is not unity, the VAMOS downlink signal is improper because its pseudo-covariance does not vanish. Secondly, in the baseband modulation stage, the symbol sequence is processed by ??/2 progressive symbol rotation and linearized Gaussian minimum shift keying (LGMSK) pulse shaping. Hence, intersymbol interference (ISI) is introduced. Lastly, due to tight frequency reuse in most GSM networks today, mobile stations also experience co-channel interference (CCI) from other base stations transmitting various types of signals such as GMSK, 8 phase shift keying (8PSK), or VAMOS. In order to achieve network capacity increase, advanced equalizers in mobile stations are required to offer superior bit error rate (BER) performance in this challenging mobile radio system.
Unlike uplink transmission where a base station is typically equipped with an antenna array to enhance the desired signal and suppress CCI, equalizer design in downlink direction is more challenging because most mobile stations have one antenna only. In the past decade, various single antenna interference cancellation (SAIC) solutions have been developed to mitigate the CCI effect. While these solutions can be straightforwardly reused to obtain acceptable performance in VAMOS, in this work a novel equalizer is proposed to achieve better BER performance by addressing the forementioned characteristics of VAMOS downlink signals. This equalizer consists of a widely linear multiple-input multiple-output (MIMO) minimum mean square error (MMSE) filter and a joint maximum likelihood sequence estimator (JMLSE). In the first stage, since the transmitted signal and the received signal may not be jointly proper, a widely linear filter is more effective in suppressing interference from other base stations plus background noise while preserving the two paired VAMOS users??? signal energy. In the next stage, further interference cancellation is achieved by jointly detecting the two users??? symbol sequences using JMLSE. Optimality of the proposed equalizer is justified by theoretical proof and simulation in this work.
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Liu, Yu-Chia, and 劉育嘉. "Reduced-Rank MMSE Combiner in Asynchronous MC-DS-CDMA System." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/85950764608541417016.
Full textAbstract:
碩士國立清華大學
電機工程學系
96
In wireless communication, a signal is impaired by interference, multipath fading and channel noise. Diversity techniques can be used to reduce these impairments. In this thesis, an asynchronous multicarrier direct sequence code division multiple access (MC-DS-CDMA) system is addressed, and the minimum mean square error (MMSE) combiner is adopted as the diversity combining technique. As the combiner is dependent on a number of factors, including the spreading codes, channel fading coefficients, and relative delays among users, it needs to be computed from symbol to symbol. Therefore, it is desirable to have a reduced-complexity method for obtaining the combiner. A reduced-rank approach is employed in this thesis. The received signal is projected to the Krylov subspace, and the projection on the subspace is used as the observation to obtain a reduced-rank MMSE combiner. It is found that this reduced-rank combiner converges to a deterministic filter in a large system. The deterministic combiner obtained in the large system assumption is used as the approximation for the combiner in a finite-size system. Thus, there is no need to re-compute the combiner at every symbol. From the simulation results, it is found that the performance loss due to this approximated combiner is negligible.
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Jhou, Jyun-An, and 周俊安. "Design of Reduced-Rank MMSE Combiner in MC-DS-CDMA." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/92659957233096862169.
Full textAbstract:
碩士國立清華大學
通訊工程研究所
96
When using full-rank MMSE combiner to detect signals in an asynchronous code-division multiple access(CDMA) system, the inverse of channel crosscorrelation matrix must be calculated. Because the matrix is related to spreading sequences, channel fading coefficients and user delay, it must be re-calculated each time a new symbol is transmitted. Due to this reason, the calculation complexity is not satisfactory. Later on, someone proposed reduced-rank MMSE combiner which can reduce the dimension used when calculating the inverse matrix by using MMSE criterion and the idea about projecting the signals onto the Krylov subspace. However, the weights of the proposed combiner still relate tightly with spreading sequence and channel realizations. Thus, the calculation complexity can not be greatly decreased because the weights still need to update with time. For further complexity reduction, asymptotic reduced-rank MMSE combiner is proposed.It has been shown that it can be used to replace real reduced-rank MMSE combiner when user number K and spreading gain N both tend to infinity. The performance measurements of the former, such as BER and Output SINR is close to the latter, and one important advantage of the former is that it can reduce the calculation complexity greatly. Because the above statements has been shown in direct-sequence CDMA (DS-CDMA) and multi-carrier CDMA (MC-CDMA), we will calculate the weights of the asymptotic reduced-rank MMSE in asynchronous MC-DS-CDMA, and different K/N and different channel fading distributions will be used in simulation. Finally, we will compare the performance of asymptotic reduced-rank MMSE combiner, real reduced-rank MMSE combiner and full-rank MMSE combiner, and then put forward the conclusion.
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Peng, Ta-Wei, and 彭達煒. "MMSE Detection for MC-CDMA and SC-FDE-CDMA System." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/22788656832390427829.
Full textAbstract:
碩士國立成功大學
電腦與通信工程研究所
97
With the increasing requirements of next generation wireless communication system for all kinds of real- time multimedia service and the rapid development of the internet, broadband wireless communication has become a full potential in the development of wireless communication. OFDM (Orthogonal Frequency Division Multiplexing) and SC-FDE (Single Carrier Transmission with Frequency Domain Equalization) was proposed to be the key physical technologies in IEEE 802.16a standard. Meanwhile, these two schemes belong to the key technologies of the forth Generation mobile communication. OFDM is a kind of multi-carrier modulation technology with outstanding benefits of high frequency efficiency, strong anti-multi-path interfere ability, easiness for equalization, etc. Its main defects lie on its sensitivity to frequency synchronization and high PAPR (Peak Average Power Rate). SC-FDE is not the same as the traditional single carrier transmitting technologies. SC-FDE transmits in groups and equalizes in frequency domain. OFDM and SC-FDE technologies have similarities as well as different points. We described the basic principle of MC-CDMA and SC-FDE systems and also made a comparison to them in the paper. The contents include the following three parts. The first one includes the second and the third chapter, we made a comparison to the several common OFDM-CDMA technologies, then proposed MC-CDMA system model in Jakes-Raleigh channel and gave the equalizer coefficient expression in MMSE rule and the system reception module for equalization-dispreading combing. The second part is the fourth chapter, in which we gave the system module of SC-FDE-CDMA system and deduced the performance for equalization-dispreading combing or dividing. The third part is chapter five, we set a system simulation environment in matlab and made a simulation and analysis for the two technologies.