Browsing by Subject "Cramer-rao lower bound (CRLB)"
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Item Open Access Fundamental limits and improved algorithms for linear least-squares wireless position estimation(John Wiley & Sons, 2010-09-22) Guvenc, I.; Gezici, Sinan; Sahinoglu Z.In this paper, theoretical lower bounds on performance of linear least-squares (LLS) position estimators are obtained, and performance differences between LLS and nonlinear least-squares (NLS) position estimators are quantified. In addition, two techniques are proposed in order to improve the performance of the LLS approach. First, a reference selection algorithm is proposed to optimally select the measurement that is used for linearizing the other measurements in an LLS estimator. Then, a maximum likelihood approach is proposed, which takes correlations between different measurements into account in order to reduce average position estimation errors. Simulations are performed to evaluate the theoretical limits and to compare performance of various LLS estimators.Item Open Access Theoretical limits on time delay estimation for ultra-wideband cognitive radios(IEEE, 2008-09) Gezici, Sinan; Celebi, H.; Arslan, H.; Poor, H. V.In this paper, theoretical limits on time delay estimation are studied for ultra-wideband (UWB) cognitive radio systems. For a generic UWB spectrum with dispersed bands, the Cramer-Rao lower bound (CRLB) is derived for unknown channel coefficients and carrier-frequency offsets (CFOs). Then, the effects of unknown channel coefficients and CFOs are investigated for linearly and non-linearly modulated training signals by obtaining specific CRLB expressions. It is shown that for linear modulations with a constant envelope, the effects of the unknown parameters can be mitigated. Finally, numerical results, which support the theoretical analysis, are presented. © 2008 IEEE.