The generation and propagation of fluorescence light within biological tissue offers the potential for biomedical diagnostics and analyte sensing. Arising from an exogenous fluorescent dye injected as a contrast agent or immobilized in a polymer implant, the fluorescent decay kinetics can be sensitive to the tissue??s biochemical environment, providing quantitative in vivo information of the confined tissue site. The impact of light propagation and decay kinetics upon the measured signals is important for consideration, simply because tissue scatters light, giving rise to nanosecond photon time-of-flights that are comparable to fluorescence relaxation kinetics. The goal of this study is to develop a time-dependent model describing (i) the generation of fluorescence from dyes exhibiting multi-exponential or more complex kinetics and (ii) its propagation in scattering media. In the preliminary study, fluorescence lifetime spectroscopy is investigated in tissue-like scattering solution. Two fluorescent dyes, 3,3-diethylthiatricarbocyanine iodide (DTTCI) and Indocynanine Green (ICG), which exhibit distinctly different lifetimes and each exhibits single-exponential decay kinetics, were employed. Measurements of phase-modulation as a function of modulation frequency were made at varying concentration ratios of the two dyes to experimentally simulate fluorescence multi-exponential decay kinetics in non-scattering and scattering solutions. The results suggest that frequency-domain measurements of fluorescent decay kinetics along with models of light propagation may be enhanced by scatter in order to probe kinetics more sensitively than in non-scattering solutions. The next study involved fluorescence lifetime sensing in scattering and non-scattering solutions with a pH sensitive dye, Carboxy Seminaphthofluorescein-1 (C-SNAFL-1), which is known to exhibit multi-exponential decay kinetics. The results demonstrate accurate pH sensing in scattering solution via fluorescence kinetics using a simplified propagation model incorporating an average lifetime. Finally, fluorescence lifetime sensing in immobilized systems were investigated. C-SNAFL-1 was immobilized in poly(ethylene glycol) (PEG) microparticles that were immersed in buffered polystyrene solutions. The results demonstrate the ability to perform pH sensing with fluorescence lifetime without the confounding effect of fluorophore loading or the use of 'reference' measurement within multiply scattering systems. In addition, the stability of the immobilized fluorescence sensor and the reliability of fluorescence lifetime measurement verify the prospect of this technology for implantable purposes.

Conventionally, the free distance is taken as the principle criterion for computing the error of convolutional and linear block codes. In other words, a larger free distance implies a better correction ability for the error correction codes. Distance spectrum is also an important factor for Maximum likelihood decoding. In this thesis, distance spectrum for different convolutional codes and CPM systems are investigated by us. Experiments results has demonstrate that a better correction ability of a shorter free distance does exist in some cases if they have a better distance spectrum. We also improve the fast algorithm for computing the distance spectrum developed by M. Cedervall and R. Johannesson. Their success is based upon the strategy of a traveling along the coding tree to find the distance spectrum. However, they need a new traveling for ever new distance computation. In contrast, we compute all the distance spectrum just in one travel by taking the advantage of the storing nodes of previous distance computation.

Combined coding with modulation is an important topic. It is verified in this thesis that a combined decoder and demodulation Viterbi receiver has a better error probability than a cascade of two separate Viterbi decoder and demodulator. Conventionally, the free distance is taken as the principle criterion for computing the error probability for coding or modulation. In many cases, distance spectrum needs to be provided for analyze the Maximum likelihood decoding. However, it is difficult for computing the distance spectrum for a combined coding with modulation because of a nonlinear structure inside. In this thesis, we first build an augmented trellis for the combined coding with modulation. Applying the concept of difference by exclusive OR and regular subtraction to the augmented trellis, we build an improved virtual trellis. As a consequence the distance spectrum for our problem can be computed because of the linear structure of the virtual trellis. The distance spectrum for different convolutional codes and CPM systems are investigated by us. Experiments results have demonstrate that a better distance spectrum implies a better error ability.

Combined coding with modulation is an important topic. Conventionally, the free distance is taken as the principle criterion for computing the error probability for coding or modulation. In many cases, distance spectrum needs to be provided for analyze the Maximum likelihood decoding. However, it is difficult for computing the distance spectrum for a combined coding with modulation because of a nonlinear structure inside. In this thesis, we study the order of distance spectrum members to find some limited number of members to present the whole distance spectrum. In our previous work, we have built an augmented trellis for the combined coding with modulation. Applying the concept of difference by exclusive OR and regular subtraction to the augmented trellis, we build an improved virtual trellis. In this thesis, we expend the concept of subtraction to a pair relation. Thus, this augmented trellis is first composed of paired states and transition lines. Then, we use a partition principle to group the states and lines. Finally, the complex trellis is reduced to a reasonable structure. We therefore can apply distance spectrum computing algorithm to find the distance spectrum. The distance spectrum for different convolution codes and CPM systems are investigated by us. Experiments results have demonstrate this distance spectrum is more accurate than before.

Signal model and observation model are commonly used to describe a dynamic system model in system identification or estimation such as Kalman filtering. The signal model is usually described by a linear dynamical equation driven by generating noise. The observation model is composed of a linear transformed signal and an additive white Gaussian noise. In this thesis, we set the generating noise to be a white binary sequence. This discrete generating noise makes the generating signal to be discrete. In contrast, the conventional generating signal is continuous. Discrete signal is simpler than the continuous signal. However, there still are too many states for this discrete signal. Therefore, defining the states and reducing the number of states are important in our work. In this thesis, we apply the tree structure to define the states. The number of states is reduced by focusing on the most probable working states. Afterwards, we apply two methods to recover the white sequence using the observation data. One is the Viterbi method; the other is Extended Kalman filter. Both methods are based upon the concept of signal states. Finally, we compare the error rates with the signal generated by continues phase modulation method.

The generation and propagation of fluorescence light within biological tissue offers the potential for biomedical diagnostics and analyte sensing. Arising from an exogenous fluorescent dye injected as a contrast agent or immobilized in a polymer implant, the fluorescent decay kinetics can be sensitive to the tissue??s biochemical environment, providing quantitative in vivo information of the confined tissue site. The impact of light propagation and decay kinetics upon the measured signals is important for consideration, simply because tissue scatters light, giving rise to nanosecond photon time-of-flights that are comparable to fluorescence relaxation kinetics. The goal of this study is to develop a time-dependent model describing (i) the generation of fluorescence from dyes exhibiting multi-exponential or more complex kinetics and (ii) its propagation in scattering media. In the preliminary study, fluorescence lifetime spectroscopy is investigated in tissue-like scattering solution. Two fluorescent dyes, 3,3-diethylthiatricarbocyanine iodide (DTTCI) and Indocynanine Green (ICG), which exhibit distinctly different lifetimes and each exhibits single-exponential decay kinetics, were employed. Measurements of phase-modulation as a function of modulation frequency were made at varying concentration ratios of the two dyes to experimentally simulate fluorescence multi-exponential decay kinetics in non-scattering and scattering solutions. The results suggest that frequency-domain measurements of fluorescent decay kinetics along with models of light propagation may be enhanced by scatter in order to probe kinetics more sensitively than in non-scattering solutions. The next study involved fluorescence lifetime sensing in scattering and non-scattering solutions with a pH sensitive dye, Carboxy Seminaphthofluorescein-1 (C-SNAFL-1), which is known to exhibit multi-exponential decay kinetics. The results demonstrate accurate pH sensing in scattering solution via fluorescence kinetics using a simplified propagation model incorporating an average lifetime. Finally, fluorescence lifetime sensing in immobilized systems were investigated. C-SNAFL-1 was immobilized in poly(ethylene glycol) (PEG) microparticles that were immersed in buffered polystyrene solutions. The results demonstrate the ability to perform pH sensing with fluorescence lifetime without the confounding effect of fluorophore loading or the use of 'reference' measurement within multiply scattering systems. In addition, the stability of the immobilized fluorescence sensor and the reliability of fluorescence lifetime measurement verify the prospect of this technology for implantable purposes.

Thesis (Ph.D.)--University of Central Florida, 2008. / Adviser: Peter J. Delfyett, Jr. Includes bibliographical references (p. 123-130).

Space-time coded systems developed in the last ten years have been designed primarily using linear modulation. Non-linear continuous phase modulation has desirable constant envelope properties and considerable potential in space-time coded systems. The work in this thesis is focussed on developing and analysing an integrated space-time coded continuous phase modulated (STC-CPM) system. The coding of the space-time encoder and the modulation is incorporated into a single trellis encoder. This allows state combining, which leads to complexity reduction due to the reduced number of states. Design criteria for STC-CPM are summarized and the Euclidean distance is shown to be important for code design. The integrated STC-CPM system design enables systematic spacetime code searches that find optimal space-time codes, to be easily implemented. Optimal rate-1/2 and rate-2/3 space-time codes are found by maximizing the system's minimum squared Euclidean distance. These codes can provide high throughput and good coding gains over un-optimized full rank codes, such as delay diversity, in a quasi-static flat fading environment. Performance bounds are developed using a union bound argument and the pairwise error probability. Approximations of the bounds are evaluated. These truncated upper bounds predict the slopes of the simulated performance curves at low error rates.

Thesis (M.S.)--Brigham Young University. Dept. of Electrical and Computer Engineering, 2005. / Includes bibliographical references (p. 67-70).

Thesis (Ph. D.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xiv, 161 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 152-161).